Pioneer Series Trust V N-CSRSCertified semi-annual shareholder report (management investment company)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number

811-21823

Pioneer Series Trust V

(Exact name of registrant as specified in charter)

60 State Street, Boston, MA 02109

(Address of principal executive offices) (ZIP code)

Terrence J. Cullen, Amundi Asset Management, Inc.,

60 State Street, Boston, MA 02109

(Name and address of agent for service)

Registrant’s telephone number, including area code:  (617) 742-7825

Date of fiscal year end:  August 31, 2022

Date of reporting period: September 1, 2021 through February 28, 2022

Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1).  The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-CSR unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609.  The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507.

Pioneer Global Sustainable Equity Fund

(Formerly, Pioneer Global Equity Fund)

Semiannual Report | February 28, 2022

visit us: www.amundi.com/us

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 1

Table of Contents

President’s Letter

Dear Shareholders,

For two years now, investors have faced unprecedented challenges, as the COVID-19 pandemic has not only dominated the headlines since March 2020, but has also led to significant changes in government and central-bank policies, both in the US and abroad, and affected the everyday lives of each of us. With 2022 now well underway, the situation, while improved, has continued to evolve.

Widespread distribution of the COVID-19 vaccines approved for emergency use in late 2020 led to a general decline in virus-related hospitalizations in the US and had a positive effect on overall market sentiment during most of the 2021 calendar year. The passage of two additional fiscal stimulus packages by US lawmakers in December 2020 and January 2021 also helped drive a strong market rally. Then, the late-2021 emergence of the highly infectious Omicron variant of the virus led to surges in cases and hospitalizations, especially outside of the US, but also in certain areas of this country. That development contributed to a slowdown in the global economic recovery, as some foreign governments reinstated strict virus-containment measures that had been relaxed after the rollout of the vaccines. Many of those renewed restrictions were lifted as case numbers again began to decline during the late-winter months, but it appears the possibility of further virus-containment measures could be with us for a while longer, given that occasional surges in new cases have continued to arise, particularly in non-US locations.

In the US, while performance of most asset classes, especially equities, was positive for the full 2021 calendar year, 2022, so far, has featured a less-friendly market environment, as volatility has remained high. Concerns over global supply chain issues, rising inflation, “hawkish” signals concerning less-accommodative future monetary policies from the Federal Reserve System (Fed), and partisan debates in Washington, DC over future spending and tax policies, are among the many factors that have led to greater uncertainty and an increase in market volatility. In addition, Russia's recent incursion into Ukraine has resulted in even greater market volatility, as economic sanctions placed on Russia by many Western countries have exacerbated the existing supply-chain issues and helped drive energy prices, including gas prices, to very high levels.

Despite those issues, and some of the recent difficulties that have affected the economy and the markets, we believe the distribution of the COVID-19 vaccines has provided a potential light at the end of the pandemic tunnel. With that said, the long-term impact on the global economy from COVID-19, while currently unknown, is likely to be considerable, as it is clear that several industries have already felt greater effects than others, and could continue to struggle for quite some time. Of course, geopolitical concerns, whether they are related to the conflict in Ukraine or other crises in different areas of the globe, can always have an effect on the markets, and so our investment teams will remain vigilant and continue to monitor the geopolitical landscape.

2 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

After leaving our offices in March of 2020 due to COVID-19, we have re-opened our US locations, but are maintaining all the necessary precautions, which at times may have us working more remotely than in person in order to ensure a safe working environment as new variants of the COVID-19 virus continue to arise and spread. I am proud of the careful planning that has taken place. Throughout the pandemic, our business has continued to operate without any disruption, and we all look forward to regaining a bit of normalcy after so many months of remote working.

Since 1928, Amundi US’s investment process has been built on a foundation of fundamental research and active management, principles which have guided our investment decisions for more than 90 years. We believe active management – that is, making active investment decisions – can help mitigate the risks during periods of market volatility.

At Amundi US, active management begins with our own fundamental, bottom-up research process. Our team of dedicated research analysts and portfolio managers analyzes each security under consideration, communicating directly with the management teams of the companies issuing the securities and working together to identify those securities that best meet our investment criteria for our family of funds. Our risk management approach begins with each and every security, as we strive to carefully understand the potential opportunity, while considering any and all risk factors.

Today, as investors, we have many options. It is our view that active management can serve shareholders well, not only when markets are thriving, but also during periods of market stress.

As you consider your long-term investment goals, we encourage you to work with your financial professional to develop an investment plan that paves the way for you to pursue both your short-term and long-term goals.

We greatly appreciate the trust you have placed in us and look forward to continuing to serve you in the future.

Sincerely,

Lisa M. Jones
Head of the Americas, President and CEO of US
Amundi Asset Management US, Inc.
April 2022

Any information in this shareowner report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 3

Portfolio Management Discussion | 2/28/22

In the following interview, portfolio managers Marco Pirondini, John Peckham, and Brian Chen discuss the factors that influenced the performance of Pioneer Global Sustainable Equity Fund* during the six-month period ended February 28, 2022. Mr. Pirondini, Senior Managing Director, Head of Equities, US, and a portfolio manager at Amundi Asset Management US, Inc. (Amundi US), Mr. Peckham, a senior vice president and a portfolio manager at Amundi US, and Mr. Chen, a vice president and a portfolio manager at Amundi US, are responsible for the day-to-day management of the Fund.

4 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

China saw a resurgence in COVID-19 cases, while instability in the country’s property markets rekindled investors’ concerns over a slowdown in global economic growth.

The fourth quarter of 2021 featured stronger market conditions. Despite the emergence of the Omicron COVID-19 variant as well as sustained inflationary pressures, evidence that the latest variant's negative health effects were less severe than those of previous COVID-19 strains helped bolster investor sentiment, particularly in the US and Europe. Markets in Asia faced more challenges, however, including new pandemic-related travel restrictions in Japan and regulatory clampdowns in China, all of which resulted in a slump in stock performance in the region for the fourth quarter.

Late in the period (early 2022), stock market performance once again declined and most major indices ended up generating flat to slightly negative returns for the full six-month period. Central banks in many countries changed their stance regarding the presence of persistently high inflation, and began viewing rising prices as a potentially sustained, rather than transitory, situation. In response to the inflationary pressures, the US Federal Reserve (Fed), after announcing that it was doubling the pace of the “tapering” of its monthly bond purchases, also signaled its intention to begin increasing the target range of the benchmark federal funds rate in March 2022, after completing the tapering of the bond purchases. Other central banks began to take similar positions with regard to tightening monetary policy.

In addition, rising geopolitical tensions over the course of the six-month period reached a peak with the Russian invasion of Ukraine in late February, which helped drive global stock markets sharply lower. At period-end, the combination of heightened geopolitical uncertainty, substantial increases in energy prices, and ongoing concerns about global macroeconomic conditions had dampened investors’ enthusiasm for riskier assets, including global equities.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 5

invest the Fund in companies that have not only been benefiting from operating efficiencies, as reflected in factors that include increased market share and revenues, but also in those that employ their capital efficiently. In particular, we emphasize strong free cash flow, because we believe that may provide companies with the flexibility to make share buybacks, reinvest in their businesses, make acquisitions, and raise dividends***.

We also look for stocks with attractive dividend yields as well as those trading at lower-than-market valuations.

Finally, we attempt to assess not only the potential price gains for each stock, but also the potential for a decline in price if circumstances become unfavorable. We prefer to invest in stocks of companies that we think have the highest potential upside relative to their downside.

Previously, Amundi US had integrated ESG considerations into its analysis, but with the name change this past February, ESG has become, by prospectus, an official part of the Fund’s investment approach. We believe that investing in companies with what we view as sustainable business models may help the Fund continue to pursue favorable performance over the long run.

Specifically, under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of borrowings, if any, for investment purposes) in securities of issuers that Amundi US believes adhere to the Fund's ESG criteria. For purposes of the 80% investment policy, “ESG criteria” is defined as the exclusion of investments issued by companies significantly involved in the production of tobacco products and controversial military weapons – consisting of cluster weapons, anti-personnel mines, nuclear weapons, and biological and chemical weapons – and the operation of thermal coal mines.

6 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

With regard to individual holdings, strong performers from a wide range of sectors and industries contributed to positive relative returns for the Fund over the six-month period. A position in European energy giant Shell was a key contributor to relative performance, as the company benefited from the steep increase in oil prices throughout the period. Canadian diversified natural resources firm Teck Resources was another positive contributor to the Fund’s relative results for the period, as the company’s focus on key industrial metals such as copper and zinc, as well as “steelmaking” coal, put it in a strong position to benefit from improving economic growth and rising commodities prices. Hensoldt, a German aerospace-and-defense company, aided the Fund’s relative performance in the latter part of the six-month period, as the stock price rose due to increased geopolitical tensions stemming from the Russia/Ukraine conflict. The Fund’s position in US bank Wells Fargo likewise benefited relative returns, as investors responded positively to the company’s strong financial results as well as prospects for improved net interest income as Treasury yields move higher. Finally, shares of AbbVie performed well over the period, boosted by strong sales of its immunology and oncology treatments.

Conversely, key detractors from the Fund’s benchmark-relative results among individual stock holdings over the period included positions in two Russian companies: energy specialist Rosneft Oil, and food-and-consumer goods retailer Magnit. Both stocks fell sharply near the end of the period in the wake of sanctions imposed against Russia by Western governments in response to the country’s invasion of Ukraine. We have retained both positions in the portfolio as of period-end. Also, the Fund's exposure to

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 7

Chinese internet and e-commerce giant Alibaba continued to weigh on relative performance, as the Chinese government's tightening of restrictions on many major technology companies added to investors’ concerns that US stock exchanges might eventually delist Chinese companies. The Fund's underweight position in Apple was another key detractor from relative performance, as the company posted solid gains during the period. Lastly, an overweight portfolio position in US e-commerce platform provider eBay detracted from the Fund’s relative results, as the company’s revenues and user base began to decline following a heightened period of activity in the earlier stages of the COVID-19 pandemic.

As the period progressed, we saw the emergence of new economic headwinds that confirmed our view that the path to a full recovery might be uneven across different regions. As noted earlier, the Fed and other central banks signaled future adoption of less-dovish monetary policies, and inflationary pressures grew more persistent in light of extended labor shortages as well as other factors.

8 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Near the end of the period, hostilities between Ukraine and Russia joined the lingering, if diminished, COVID-19 pandemic and changing monetary policies as catalysts for market volatility. As a result, we believe higher energy prices could further exacerbate the pre-existing inflationary pressures, and could slow global economic activity. Despite those issues, however, our base case is for a continuation of the economic expansion going forward.

Because of those factors, we have overweighted the portfolio to what we view as the high-quality value/cyclical areas of the market. Conversely, we have significantly underweighted the Fund to high-momentum growth stocks, and have minimized the portfolio's exposures to stocks of deep/distressed value companies with more-leveraged balance sheets, as we think such companies could face significant risks to future earnings.

From a geographic standpoint, some of the Fund’s most significant overweight allocations are in countries located in northeast Asia, including Japan and Korea, due to the significant valuation discounts we have seen in those markets. We have retained the portfolio’s exposures to European stocks, as we have sought to take advantage of what we view as attractive valuations in a region where the local economies could stand to benefit from an ongoing economic recovery. The US remains the country with the largest exposure in the portfolio on an absolute basis, a reflection of the strong economic recovery there, and healthy US consumer balance sheets. However, due to valuation concerns, we have continued to underweight the Fund to US large-cap growth technology stocks.

From a sector perspective, the Fund ended the six-month period with benchmark-relative overweights to sectors featuring companies that we feel could be positioned to benefit if our macroeconomic view turns out to be correct over the long run. Those sectors include financials, energy, and materials. Finally, the Fund has remained underweight to communication services, real estate, and utilities.

Please refer to the Schedule of Investments on pages 20–25 for a full listing of fund securities.

All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility and heightened uncertainty. The market prices of securities may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions,

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 9

recessions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets, the spread of infectious illness or other public health issues, armed conflict including Russia's military invasion of Ukraine, sanctions against Russia, other nations or individuals or companies and possible countermeasures, or adverse investor sentiment. These conditions may continue, recur, worsen or spread.

Investing in foreign and/or emerging markets securities involves risks relating to interest rates, currency exchange rates, economic, and political conditions.

The Fund generally excludes corporate issuers that do not meet or exceed minimum ESG standards. Excluding specific issuers limits the universe of investments available to the Fund, which may mean forgoing some investment opportunities available to funds without similar ESG standards.

The Fund is subject to currency risk, meaning that the Fund could experience losses based on changes in the exchange rate between non-U.S. currencies and the U.S. dollar.

Investments in small- and mid-sized companies may offer the potential for higher returns, but are also subject to greater short-term price fluctuations than investments in larger, more established companies.

When interest rates rise, the prices of fixed-income securities held by the Fund will generally fall. Conversely, when interest rates fall, the prices of fixed-income securities held by the Fund will generally rise.

The Fund may use derivatives, such as options, futures, inverse floating rate obligations, swaps, and others, which can be illiquid, may disproportionately increase losses, and have a potentially large impact on Fund performance. Derivatives may have a leveraging effect on the Fund.

At times, the Fund’s investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors.

These risks may increase share price volatility.

Before investing, consider the product’s investment objectives, risks, charges and expenses. Contact your advisor or Amundi Asset Management US, Inc., for a prospectus or summary prospectus containing this information. Read it carefully.

Any information in this shareholder report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

10 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Portfolio Summary | 2/28/22

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 11

Prices and Distributions | 2/28/22

Net Asset Value per Share

Index Definitions

The Morgan Stanley Capital International (MSCI) World NR^† Index is an unmanaged measure of the performance of stock markets in the developed world. The MSCI All Country World NR Index is an unmanaged, free-float-adjusted, market-capitalization-weighted index that is designed to measure the equity market performance of developed and emerging markets, and consists of 45 country indices comprising 24 developed and 21 emerging market country indices. Index returns are calculated monthly, assume reinvestment of dividends and, unlike Fund returns, do not reflect any fees, expenses or sales charges. It is not possible to invest directly in either index.

The indices defined here pertain to the “Value of $10,000 Investment” and “Value of $5 Million Investment” charts on pages 13–17.

12 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class A shares of Pioneer Global Sustainable Equity Fund at public offering price during the periods shown, compared to that of the Morgan Stanley Capital International (MSCI) World NR Index and the MSCI All Country World NR Index.

Call 1-800-225-6292 or visit www.amundi.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

NAV results represent the percent change in net asset value per share. NAV returns would have been lower had sales charges been reflected. POP returns reflect deduction of maximum 5.75% sales charge. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results shown reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The net expense ratio reflects the contractual expense limitation in effect through January 1, 2023 for Class A shares. There can be no assurance that Amundi US will extend the expense limitation beyond such time. Please see the prospectus for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 13

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class C shares of Pioneer Global Sustainable Equity Fund during the periods shown, compared to that of the Morgan Stanley Capital International (MSCI) World NR Index and the MSCI All Country World NR Index.

Call 1-800-225-6292 or visit www.amundi.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

Class C shares held for less than one year are subject to a 1% contingent deferred sales charge (CDSC). “If Held” results represent the percent change in net asset value per share. “If Redeemed” returns reflect deduction of the CDSC for the one-year period, assuming a complete redemption of shares at the last price calculated on the last business day of the period, and no CDSC for the five- and 10-year periods. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for a more current expense ratio.

14 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Investment Returns

The mountain chart on the right shows the change in value of a $5 million investment made in Class K shares of Pioneer Global Sustainable Equity Fund during the periods shown, compared to that of the Morgan Stanley Capital International (MSCI) World NR Index and the MSCI All Country World NR Index.

Call 1-800-225-6292 or visit www.amundi.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

The performance shown for Class K shares for the period prior to the commencement of operations of Class K shares on December 31, 2014, is the net asset value performance of the Fund’s Class A shares, which has not been restated to reflect any differences in expenses, including Rule 12b-1 fees applicable to Class A shares. Since fees for Class A shares generally are higher than those of Class K shares, the performance of Class K shares prior to their inception would have been higher than the performance shown. For the period beginning December 31, 2014, the actual performance of Class K shares is reflected. Class K shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The net expense ratio reflects the contractual expense limitation in effect through January 1, 2023 for Class K shares. There can be no assurance that Amundi US will extend the expense limitation beyond such time. Please see the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 15

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class R shares of Pioneer Global Sustainable Equity Fund during the periods shown, compared to that of the Morgan Stanley Capital International (MSCI) World NR Index and the MSCI All Country World NR Index.

Call 1-800-225-6292 or visit www.amundi.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

The performance shown for Class R shares for the period prior to the commencement of operations of Class R shares on July 1, 2015, is the net asset value performance of the Fund’s Class A shares, which has not been restated to reflect any differences in expenses, including Rule 12b-1 fees applicable to Class A shares. Since fees for Class A shares generally are higher than those of Class R shares, the performance of Class R shares prior to their inception would have been higher than the performance shown. For the period beginning July 1, 2015, the actual performance of Class R shares is reflected. Class R shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The net expense ratio reflects the contractual expense limitation in effect through January 1, 2023 for Class R shares. There can be no assurance that Amundi US will extend the expense limitation beyond such time. Please see the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please see the financial highlights for more current expense ratios.

16 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Investment Returns

The mountain chart on the right shows the change in value of a $5 million investment made in Class Y shares of Pioneer Global Sustainable Equity Fund during the periods shown, compared to that of the Morgan Stanley Capital International (MSCI) World NR Index and the MSCI All Country World NR Index.

Call 1-800-225-6292 or visit www.amundi.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

Class Y shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The net expense ratio reflects the contractual expense limitation in effect through January 1, 2023 for Class Y shares. There can be no assurance that Amundi US will extend the expense limitation beyond such time. Please see the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please see the financial highlights for more current expense ratios.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 17

Comparing Ongoing Fund Expenses

As a shareowner in the Fund, you incur two types of costs:

This example is intended to help you understand your ongoing expenses (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds. The example is based on an investment of $1,000 at the beginning of the Fund’s latest six-month period and held throughout the six months.

Using the Tables

Actual Expenses

The first table below provides information about actual account values and actual expenses. You may use the information in this table, together with the amount you invested, to estimate the expenses that you paid over the period as follows:

Example: an $8,600 account value ÷ $1,000 = 8.6

During Period” to estimate the expenses you paid on your account during this period.

Expenses Paid on a $1,000 Investment in Pioneer Global Equity Fund

Based on actual returns from September 1, 2021 through February 28, 2022.

18 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Hypothetical Example for Comparison Purposes

The table below provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the Fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period.

You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the tables are meant to highlight your ongoing costs only and do not reflect any transaction costs, such as sales charges (loads) or redemption fees that are charged at the time of the transaction. Therefore, the table below is useful in comparing ongoing costs only and will not help you determine the relative total costs of owning different funds. In addition, if these transaction costs were included, your costs would have been higher.

Expenses Paid on a $1,000 Investment in Pioneer Global Equity Fund

Based on a hypothetical 5% return per year before expenses, reflecting the period from September 1, 2021 through February 28, 2022.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 19

Schedule of Investments | 2/28/22

(unaudited)

The accompanying notes are an integral part of these financial statements.

20 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 21

Schedule of Investments | 2/28/22

(unaudited) (continued)

The accompanying notes are an integral part of these financial statements.

22 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 23

Schedule of Investments | 2/28/22

(unaudited) (continued)

Distribution of investments by country of domicile (excluding short term investments) as a percentage of total investments in securities, is as follows:

Purchases and sales of securities (excluding short term investments) for the six months ended February 28, 2022, aggregated $95,828,790 and $93,781,878, respectively.

The Fund is permitted to engage in purchase and sale transactions (“cross trades”) with certain funds and accounts for which the Amundi Asset Management US, Inc. (the "Adviser") serves as the Fund's investment adviser, as set forth in Rule 17a-7 under the Investment Company Act of 1940, pursuant to procedures adopted by the Board of Trustees. Under these procedures, cross trades are effected at current market prices. During the six months ended February 28, 2022, the Fund did not engage in any cross trade activity.

At February 28, 2022, the net unrealized appreciation on investments based on cost for federal tax purposes of $250,909,642 was as follows:

Various inputs are used in determining the value of the Fund's investments. These inputs are summarized in the three broad levels below.

Level 1 – unadjusted quoted prices in active markets for identical securities.

Level 2 – other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.). See Notes to Financial Statements — Note 1A.

Level 3 – significant unobservable inputs (including the Fund's own assumptions in determining fair value of investments). See Notes to Financial Statements — Note 1A.

The accompanying notes are an integral part of these financial statements.

24 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The following is a summary of the inputs used as of February 28, 2022, in valuing the Fund's investments:

During the six months ended February 28, 2022, there were no transfers in or out of Level 3.

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 25

Statement of Assets and Liabilities | 2/28/22

(unaudited)

The accompanying notes are an integral part of these financial statements.

26 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Statement of Operations (unaudited)

FOR THE SIX MONTHS ENDED 2/28/22

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 27

Statements of Changes in Net Assets

The accompanying notes are an integral part of these financial statements.

28 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 29

The accompanying notes are an integral part of these financial statements.

30 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 31

Financial Highlights (continued)

The accompanying notes are an integral part of these financial statements.

32 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The accompanying notes are an integral part of these financial statements.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 33

Financial Highlights (continued)

The accompanying notes are an integral part of these financial statements.

34 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Notes to Financial Statements | 2/28/22

(unaudited)

1. Organization and Significant Accounting Policies

Pioneer Global Sustainable Equity Fund (the “Fund”) is one of two portfolios comprising Pioneer Series Trust V (the “Trust”), a Delaware statutory trust. The Fund is registered under the Investment Company Act of 1940 as a diversified, open-end management investment company. The Fund’s investment objective is to seek long-term capital growth. Prior to February 15, 2022, the Fund was known as Pioneer Global Equity Fund.

The Fund offers five classes of shares designated as Class A, Class C, Class K, Class R and Class Y shares. Each class of shares represents an interest in the same portfolio of investments of the Fund and has identical rights (based on relative net asset values) to assets and liquidation proceeds. Share classes can bear different rates of class-specific fees and expenses such as transfer agent and distribution fees. Differences in class-specific fees and expenses will result in differences in net investment income and, therefore, the payment of different dividends from net investment income earned by each class. The Amended and Restated Declaration of Trust of the Trust gives the Board of Trustees the flexibility to specify either per-share voting or dollar-weighted voting when submitting matters for shareowner approval. Under per-share voting, each share of a class of the Fund is entitled to one vote. Under dollar-weighted voting, a shareowner’s voting power is determined not by the number of shares owned, but by the dollar value of the shares on the record date. Each share class has exclusive voting rights with respect to matters affecting only that class, including with respect to the distribution plan for that class. There is no distribution plan for Class K or Class Y shares.

Amundi Asset Management US, Inc., an indirect, wholly owned subsidiary of Amundi and Amundi’s wholly owned subsidiary, Amundi USA, Inc., serves as the Fund’s investment adviser (the “Adviser”). Amundi Distributor US, Inc., an affiliate of the Adviser, serves as the Fund’s distributor (the “Distributor”).

In March 2020, FASB issued an Accounting Standard Update, ASU 2020-04, Reference Rate Reform (Topic 848) — Facilitation of the Effects of Reference Rate Reform on Financial Reporting (“ASU 2020-04”), which provides optional, temporary relief with respect to the financial reporting of contracts subject to certain types of modifications due to the planned discontinuation of the London Interbank Offered Rate (“LIBOR”) and other LIBOR-based reference rates at the end of 2021. The temporary relief provided by ASU 2020-04 is effective for certain reference rate-related contract modifications that occur during the period from March 12, 2020

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 35

through December 31, 2022. Management is evaluating the impact of ASU 2020-04 on the Fund's investments, derivatives, debt and other contracts, if applicable, that will undergo reference rate-related modifications as a result of the reference rate reform.

The Fund is an investment company and follows investment company accounting and reporting guidance under U.S. Generally Accepted Accounting Principles (“U.S. GAAP”). U.S. GAAP requires the management of the Fund to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of income, expenses and gain or loss on investments during the reporting period. Actual results could differ from those estimates.

The following is a summary of significant accounting policies followed by the Fund in the preparation of its financial statements:

The net asset value of the Fund is computed once daily, on each day the New York Stock Exchange (“NYSE”) is open, as of the close of regular trading on the NYSE.

Equity securities that have traded on an exchange are valued by using the last sale price on the principal exchange where they are traded. Equity securities that have not traded on the date of valuation, or securities for which sale prices are not available, generally are valued using the mean between the last bid and asked prices or, if both last bid and asked prices are not available, at the last quoted bid price. Last sale and bid and asked prices are provided by independent third party pricing services. In the case of equity securities not traded on an exchange, prices are typically determined by independent third party pricing services using a variety of techniques and methods.

The principal exchanges and markets for non-U.S. equity securities have closing times prior to the close of the NYSE. However, the value of these securities may be influenced by changes in global markets occurring after the closing times of the local exchanges and markets up to the time the Fund determines its net asset value. Consequently, the Fund uses a fair value model developed by an independent pricing service to value non-U.S. equity securities. On a daily basis, the pricing service recommends changes, based on a proprietary model, to the closing market prices of each non-U.S.security held by the Fund to reflect the security’s fair value at the time the Fund determines its net asset value. The Fund applies these recommendations in accordance with procedures approved by the Board of Trustees.

36 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The value of foreign securities is translated into U.S. dollars based on foreign currency exchange rate quotations supplied by a third party pricing source. Trading in non-U.S. equity securities is substantially completed each day at various times prior to the close of the NYSE. The values of such securities used in computing the net asset value of the Fund's shares are determined as of such times. The Fund may use a fair value model developed by an independent pricing service to value non-U.S. equity securities.

Forward foreign currency exchange contracts are valued daily using the foreign exchange rate or, for longer term forward contract positions, the spot currency rate and the forward points on a daily basis, in each case provided by a third party pricing service. Contracts whose forward settlement date falls between two quoted days are valued by interpolation.

Futures contracts are generally valued at the closing settlement price established by the exchange on which they are traded.

Shares of open-end registered investment companies (including money market mutual funds) are valued at such funds’ net asset value. Shares of exchange-listed closed-end funds are valued by using the last sale price on the principal exchange where they are traded.

Securities for which independent pricing services or broker-dealers are unable to supply prices or for which market prices and/or quotations are not readily available or are considered to be unreliable are valued by a fair valuation team comprised of certain personnel of the Adviser pursuant to procedures adopted by the Fund's Board of Trustees. The Adviser’s fair valuation team uses fair value methods approved by the Valuation Committee of the Board of Trustees. The Adviser’s fair valuation team is responsible for monitoring developments that may impact fair valued securities and for discussing and assessing fair values on an ongoing basis, and at least quarterly, with the Valuation Committee of the Board of Trustees.

Inputs used when applying fair value methods to value a security may include credit ratings, the financial condition of the company, current market conditions and comparable securities. The Fund may use fair value methods if it is determined that a significant event has occurred after the close of the exchange or market on which the security trades and prior to the determination of the Fund's net asset value. Examples of a significant event might include political or economic news, corporate restructurings, natural disasters, terrorist activity or trading halts. Thus, the valuation of the Fund's securities may differ significantly from exchange prices, and such differences could be material.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 37

At February 28, 2022, no securities were valued using fair value methods (other than securities valued using prices supplied by independent pricing services, broker-dealers or using a third party insurance industry broker valuation model).

Dividend income is recorded on the ex-dividend date, except that certain dividends from foreign securities where the ex-dividend date may have passed are recorded as soon as the Fund becomes aware of the ex- dividend data in the exercise of reasonable diligence.

Interest income, including interest on income-bearing cash accounts, is recorded on the accrual basis. Dividend and interest income are reported net of unrecoverable foreign taxes withheld at the applicable country rates and net of income accrued on defaulted securities.

Interest and dividend income payable by delivery of additional shares is reclassified as PIK (payment-in-kind) income upon receipt and is included in interest and dividend income, respectively.

Security transactions are recorded as of trade date. Gains and losses on sales of investments are calculated on the identified cost method for both financial reporting and federal income tax purposes.

The books and records of the Fund are maintained in U.S. dollars. Amounts denominated in foreign currencies are translated into U.S. dollars using current exchange rates.

Net realized gains and losses on foreign currency transactions, if any, represent, among other things, the net realized gains and losses on foreign currency exchange contracts, disposition of foreign currencies and the difference between the amount of income accrued and the U.S. dollars actually received. Further, the effects of changes in foreign currency exchange rates on investments are not segregated on the Statement of Operations from the effects of changes in the market prices of those securities, but are included with the net realized and unrealized gain or loss on investments.

It is the Fund's policy to comply with the requirements of the Internal Revenue Code applicable to regulated investment companies and to distribute all of its net taxable income and net realized capital gains, if any, to its shareowners. Therefore, no provision for federal income taxes is required. As of August 31, 2021, the Fund did not accrue any interest or penalties with respect to uncertain tax positions, which, if applicable,

38 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

would be recorded as an income tax expense on the Statement of Operations. Tax returns filed within the prior three years remain subject to examination by federal and state tax authorities.

In addition to the requirements of the Internal Revenue Code, the Fund may also be required to pay local taxes on the recognition of capital gains and/or the repatriation of foreign currencies in certain countries.

In determining the daily net asset value, the Fund estimates the reserve for such taxes, if any, associated with investments in certain countries. The estimated reserve for the capital gains is based on the net unrealized appreciation on certain portfolio securities, the holding period of such securities and the related tax rates, tax loss carryforward (if applicable) and other such factors.

The amount and character of income and capital gain distributions to shareowners are determined in accordance with federal income tax rules, which may differ from U.S. GAAP. Distributions in excess of net investment income or net realized gains are temporary over distributions for financial statement purposes resulting from differences in the recognition or classification of income or distributions for financial statement and tax purposes. Capital accounts within the financial statements are adjusted for permanent book/tax differences to reflect tax character, but are not adjusted for temporary differences.

The tax character of distributions paid during the year ended August 31, 2021 was as follows:

The following shows the components of distributable earnings (losses) on a federal income tax basis at August 31, 2021:

The difference between book-basis and tax-basis net unrealized appreciation is attributable to the tax deferral of losses on wash sales, the mark to market of forward currency, and tax basis adjustments on partnerships.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 39

The Fund records sales and repurchases of its shares as of trade date. The Distributor earned $6,309 in underwriting commissions on the sale of Class A shares during the six months ended February 28, 2022.

Income, common expenses and realized and unrealized gains and losses are calculated at the Fund level and allocated daily to each class of shares based on its respective percentage of adjusted net assets at the beginning of the day.

Distribution fees are calculated based on the average daily net asset value attributable to Class A, Class C and Class R shares of the Fund, respectively (see Note 5). Class K and Class Y shares do not pay distribution fees. All expenses and fees paid to the Fund's transfer agent for its services are allocated among the classes of shares based on the number of accounts in each class and the ratable allocation of related out-of-pocket expenses (see Note 4).

Distributions to shareowners are recorded as of the ex-dividend date. Distributions paid by the Fund with respect to each class of shares are calculated in the same manner and at the same time, except that net investment income dividends to Class A, Class C, Class K, Class R and Class Y shares can reflect different transfer agent and distribution expense rates.

The value of securities held by the Fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political or regulatory conditions, recessions, the spread of infectious illness or other public health issues, inflation, changes in interest rates, armed conflict including Russia's military invasion of Ukraine, sanctions against Russia, other nations or individuals or companies and possible countermeasures, lack of liquidity in the bond markets or adverse investor sentiment. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. Interest rates are very low, which means there is more risk that they may go up. The U.S. Federal Reserve has recently started to raise certain interest rates. A general rise in interest rates could adversely affect the price and liquidity of fixed-income securities and could also result in increased redemptions from the Fund. Rates of inflation have recently risen. The value of assets or income from

40 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

an investment may be worth less in the future as inflation decreases the value of money. As inflation increases, the real value of the Fund’s assets can decline as can the value of the Fund’s distributions.

The global pandemic of the novel coronavirus respiratory disease designated COVID-19 has resulted in major disruption to economies and markets around the world, including the United States. Global financial markets have experienced extreme volatility and severe losses, and trading in many instruments has been disrupted. Liquidity for many instruments has been greatly reduced for periods of time. Some sectors of the economy and individual issuers have experienced particularly large losses. These circumstances may continue for an extended period of time, and may continue to affect adversely the value and liquidity of the Fund’s investments. Following Russia’s recent invasion of Ukraine, Russian securities have lost all, or nearly all, their market value. Other securities or markets could be similarly affected by past or future geopolitical or other events or conditions.

Governments and central banks, including the U.S. Federal Reserve, have taken extraordinary and unprecedented actions to support local and global economies and the financial markets. These actions have resulted in significant expansion of public debt, including in the U.S. The consequences of high public debt, including its future impact on the economy and securities markets, may not be known for some time.

At times, the Fund’s investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors.

The Fund’s investments in foreign markets and countries with limited developing markets may subject the Fund to a greater degree of risk than investments in a developed market. These risks include disruptive political or economic conditions, military conflicts and sanctions, terrorism, sustained economic downturns, financial instability, reduction of government or central bank support, inadequate accounting standards, tariffs, tax disputes or other tax burdens, nationalization or expropriation of assets, and the imposition of adverse governmental laws, arbitrary application of laws and regulations or lack of rule of law, or currency exchange restrictions.

Russia launched a large-scale invasion of Ukraine on February 24, 2022. In response to the military action by Russia, various countries, including the U.S., the United Kingdom, and European Union issued broad-ranging economic sanctions against Russia and Belarus and certain companies and individuals. Since then, Russian securities have lost all, or nearly all, their market value, and many other issuers, securities and markets have been

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 41

adversely affected. The United States and other countries may impose sanctions on other countries, companies and individuals in light of Russia’s military invasion. The extent and duration of the military action or future escalation of such hostilities, the extent and impact of existing and future sanctions, market disruptions and volatility, and the result of any diplomatic negotiations cannot be predicted. These and any related events could have a significant impact on the value and liquidity of certain Fund investments, on Fund performance and the value of an investment in the Fund, particularly with respect to securities and commodities, such as oil and natural gas, as well as other sectors with exposure to Russian issuers or issuers in other countries affected by the invasion, and are likely to have collateral impacts on market sectors globally.

With the increased use of technologies such as the Internet to conduct business, the Fund is susceptible to operational, information security and related risks. While the Fund’s Adviser has established business continuity plans in the event of, and risk management systems to prevent, limit or mitigate, such cyber-attacks, there are inherent limitations in such plans and systems, including the possibility that certain risks have not been identified. Furthermore, the Fund cannot control the cybersecurity plans and systems put in place by service providers to the Fund such as the Fund’s custodian and accounting agent, and the Fund’s transfer agent. In addition, many beneficial owners of Fund shares hold them through accounts at broker-dealers, retirement platforms and other financial market participants over which neither the Fund nor the Adviser exercises control. Each of these may in turn rely on service providers to them, which are also subject to the risk of cyber-attacks. Cybersecurity failures or breaches at the Adviser or the Fund’s service providers or intermediaries have the ability to cause disruptions and impact business operations, potentially resulting in financial losses, interference with the Fund’s ability to calculate its net asset value, impediments to trading, the inability of Fund shareowners to effect share purchases, redemptions or exchanges or receive distributions, loss of or unauthorized access to private shareowner information and violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, or additional compliance costs. Such costs and losses may not be covered under any insurance. In addition, maintaining vigilance against cyber-attacks may involve substantial costs over time, and system enhancements may themselves be subject to cyber-attacks.

The Fund’s prospectus contains unaudited information regarding the Fund’s principal risks. Please refer to that document when considering the Fund’s principal risks.

42 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

The Fund may write put and covered call options to seek to increase total return. When an option is written, the Fund receives a premium and becomes obligated to purchase or sell the underlying security at a fixed price, upon the exercise of the option. When the Fund writes an option, an amount equal to the premium received by the Fund is recorded as “Written options outstanding” on the Statement of Assets and Liabilities and is subsequently adjusted to the current value of the option written. Premiums received from writing options that expire unexercised are treated by the Fund on the expiration date as realized gains from investments on the Statement of Operations. The difference between the premium and the amount paid on effecting a closing purchase transaction, including brokerage commissions, is also treated as a realized gain on the Statement of Operations, or, if the premium is less than the amount paid for the closing purchase transaction, as a realized loss on the Statement of Operations. If a call option is exercised, the premium is added to the proceeds from the sale of the underlying security in determining whether the Fund has realized a gain or loss. The Fund as writer of an option bears the market risk of an unfavorable change in the price of the security underlying the written option.

The average market value of written options for the six months ended February 28, 2022, was $(6,776). Open written options contracts at February 28, 2022, are listed in the Schedule of Investments.

The Fund may enter into forward foreign currency exchange contracts (“contracts”) for the purchase or sale of a specific foreign currency at a fixed price on a future date. All contracts are marked-to-market daily at the applicable exchange rates, and any resulting unrealized appreciation or depreciation is recorded in the Fund's financial statements. The Fund records realized gains and losses at the time a contract is offset by entry into a closing transaction or extinguished by delivery of the currency. Risks may arise upon entering into these contracts from the potential inability of counterparties to meet the terms of the contract and from unanticipated movements in the value of foreign currencies relative to the U.S. dollar (see Note 7).

During the six months ended February 28, 2022, the Fund had entered into various forward foreign currency exchange contracts that obligated the Fund to deliver or take delivery of currencies at specified future maturity

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 43

dates. Alternatively, prior to the settlement date of a forward foreign currency exchange contract, the Fund may close out such contract by entering into an offsetting contract.

The average market value of forward foreign currency exchange contracts open during the six months ended February 28, 2022, was $0. There were no open forward foreign currency exchange contracts outstanding at February 28, 2022.

2. Management Agreement

The Adviser manages the Fund’s portfolio. Management fees payable under the Fund's Investment Management Agreement with the Adviser are calculated daily and paid monthly at the annual rate of 0.65% of the Fund’s average daily net assets up to $1 billion and 0.60% of the Fund’s average daily net assets over $1 billion. For the six months ended February 28, 2022, the effective management fee (excluding waivers and/or assumption of expenses) was equivalent to 0.65% (annualized) of the Fund’s average daily net assets.

The Adviser has contractually agreed to limit ordinary operating expenses (ordinary operating expenses means all fund expenses other than taxes, brokerage commissions, acquired fund fees and expenses, and extraordinary expenses, such as litigation) to the extent required to reduce Fund expenses to 1.15%, 2.15%, 0.70%, 1.55% and 0.70% of the average daily net assets attributable to Class A, Class C, Class K, Class R and Class Y shares, respectively. These expense limitations are in effect through January 1, 2023. There can be no assurance that the Adviser will extend the expense limitation agreement for a class of shares beyond the date referred to above. Fees waived and expenses reimbursed during the six months ended February 28, 2022 are reflected on the Statement of Operations.

In addition, under the management and administration agreements, certain other services and costs, including accounting, regulatory reporting and insurance premiums, are paid by the Fund as administrative reimbursements. Included in “Due to affiliates” reflected on the Statement of Assets and Liabilities is $26,607 in management fees, administrative costs and certain other reimbursements payable to the Adviser at February 28, 2022.

3. Compensation of Trustees and Officers

The Fund pays an annual fee to its Trustees. The Adviser reimburses the Fund for fees paid to the Interested Trustees. For the six months ended February 28, 2022, the Fund paid $4,597 in Trustees’ compensation, which is reflected on Statement of Operations as Trustees’ fees. At February 28, 2022, the Fund had a payable for Trustees’ fees on its Statement of Assets and Liabilities of $1,604.

44 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

4. Transfer Agent

For the period from September 1, 2021 to November 21, 2021, DST Asset Manager Solutions, Inc. served as the transfer agent to the Fund at negotiated rates. Effective November 22, 2021, BNY Mellon Investment Servicing (US) Inc. serves as the transfer agent to the Fund at negotiated rates. Transfer agent fees and payables shown on the Statement of Operations and the Statement of Assets and Liabilities, respectively, include sub-transfer agent expenses incurred through the Fund’s omnibus relationship contracts.

In addition, the Fund reimbursed the transfer agent for out-of-pocket expenses incurred by the transfer agent related to shareowner communications activities such as proxy and statement mailings, and outgoing phone calls. For the six months ended February 28, 2022, such out-of-pocket expenses by class of shares were as follows:

5. Distribution and Service Plans

The Fund has adopted a distribution plan (the “Plan”) pursuant to Rule 12b-1 of the Investment Company Act of 1940 with respect to its Class A, Class C and Class R shares. Pursuant to the Plan, the Fund pays the Distributor 0.25% of the Fund's average daily net assets attributable to Class A shares as compensation for personal services and/or account maintenance services or distribution services with regard to Class A shares. Pursuant to the Plan, the Fund also pays the Distributor 1.00% of the average daily net assets attributable to Class C shares. The fee for Class C shares consists of a 0.25% service fee and a 0.75% distribution fee paid as compensation for personal services and/or account maintenance services or distribution services with regard to Class C shares. Pursuant to the Plan, the Fund further pays the Distributor 0.50% of the average daily net assets attributable to Class R shares for distribution services. Included in “Due to affiliates” reflected on the Statement of Assets and Liabilities is $13,780 in distribution fees payable to the Distributor at February 28, 2022.

The Fund also has adopted a separate service plan for Class R shares (the “Service Plan”). The Service Plan authorizes the Fund to pay securities dealers, plan administrators or other service organizations that agree to

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 45

provide certain services to retirement plans or plan participants holding shares of the Fund a service fee of up to 0.25% of the Fund’s average daily net assets attributable to Class R shares held by such plans.

In addition, redemptions of Class A and Class C shares may be subject to a contingent deferred sales charge (“CDSC”). A CDSC of 1.00% may be imposed on redemptions of certain net asset value purchases of Class A shares within 12 months of purchase. Redemptions of Class C shares within 12 months of purchase are subject to a CDSC of 1.00% based on the lower of cost or market value of shares being redeemed. Shares purchased as part of an exchange remain subject to any CDSC that applied to the original purchase of those shares. There is no CDSC for Class K, Class R or Class Y shares. Proceeds from the CDSCs are paid to the Distributor. For the six months ended February 28, 2022, CDSCs in the amount of $843 were paid to the Distributor.

6. Line of Credit Facility

The Fund, along with certain other funds in the Pioneer Family of Funds, participates in a committed, unsecured revolving line of credit (“credit facility”). Borrowings are used solely for temporary or emergency purposes. The Fund may borrow up to the lesser of the amount available under the credit facility or the limits set for borrowing by the Fund’s prospectus and the 1940 Act. Effective February 2, 2022, the Fund participates in a facility in the amount of $380 million. Prior to February 2, 2022, the Fund participated in a facility in the amount of $450 million. Under such facility, depending on the type of loan, interest on borrowings is payable at the London Interbank Offered Rate (“LIBOR”) plus a credit spread. The Fund also pays both an upfront fee and an annual commitment fee to participate in the credit facility. The upfront fee in the amount of 0.10% of the total credit facility and the commitment fee in the amount of 0.25% of the daily unused portion of each lender's commitment are allocated among participating funds based on an allocation schedule set forth in the credit agreement. For the six months ended February 28, 2022, the Fund had no borrowings under the credit facility.

7. Additional Disclosures about Derivative Instruments and Hedging Activities

The Fund’s use of derivatives may enhance or mitigate the Fund’s exposure to the following risks:

Interest rate risk relates to the fluctuations in the value of interest-bearing securities due to changes in the prevailing levels of market interest rates.

46 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Credit risk relates to the ability of the issuer of a financial instrument to make further principal or interest payments on an obligation or commitment that it has to the Fund.

Foreign exchange rate risk relates to fluctuations in the value of an asset or liability due to changes in currency exchange rates.

Equity risk relates to the fluctuations in the value of financial instruments as a result of changes in market prices (other than those arising from interest rate risk or foreign exchange rate risk), whether caused by factors specific to an individual investment, its issuer, or all factors affecting all instruments traded in a market or market segment.

Commodity risk relates to the risk that the value of a commodity or commodity index will fluctuate based on increases or decreases in the commodities market and factors specific to a particular industry or commodity.

The fair value of open derivative instruments (not considered to be hedging instruments for accounting disclosure purposes) by risk exposure at February 28, 2022, was as follows:

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 47

The effect of derivative instruments (not considered to be hedging instruments for accounting disclosure purposes) on the Statement of Operations by risk exposure at February 28, 2022 was as follows:

8. Changes in Custodian and Sub-Administrator, and Transfer Agent

Effective November 22, 2021, The Bank of New York Mellon Corporation (“BNY Mellon”) serves as the Fund's Custodian and Sub-Administrator.

Effective November 22, 2021, BNY Mellon Investment Servicing (US) Inc. serves as the Fund's shareholder servicing and transfer agent.

9. Changes to the Fund's Name and Principal Investment Strategies

Effective February 15, 2022, the Fund’s name changed to “Pioneer Global Sustainable Equity Fund.”

Effective February 15, 2022, in making investments, Amundi US seeks to identify companies with sustainable business models, including by evaluating environmental, social and governance (ESG) practices. In keeping with this focus, the Fund applies ESG criteria to its investments. Under normal circumstances, the Fund invests at least 80% of its net assets (plus the amount of borrowings, if any, for investment purposes) in securities of issuers that Amundi US believes adhere to the Fund’s ESG criteria.

For purposes of the 80% investment policy, “ESG criteria” is defined as the exclusion of investments issued by companies significantly involved in the production of tobacco products and controversial military weapons, consisting of cluster weapons, anti-personnel mines, nuclear weapons, and biological and chemical weapons, and the operation of thermal coal mines. To the extent possible on the basis of information available to Amundi US, an issuer will be deemed to be significantly involved in an activity if it derives more than 10% of its gross revenues from such activities.

48 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Approval of Renewal of Investment Management Agreement

Amundi Asset Management US, Inc. (“Amundi US”) serves as the investment adviser to Pioneer Global Sustainable Equity Fund (the “Fund”) pursuant to an investment management agreement between Amundi US and the Fund. In order for Amundi US to remain the investment adviser of the Fund, the Trustees of the Fund, including a majority of the Fund’s Independent Trustees, must determine annually whether to renew the investment management agreement for the Fund.

The contract review process began in January 2021 as the Trustees of the Fund agreed on, among other things, an overall approach and timeline for the process. Contract review materials were provided to the Trustees in March 2021, July 2021 and September 2021. In addition, the Trustees reviewed and discussed the Fund’s performance at regularly scheduled meetings throughout the year, and took into account other information related to the Fund provided to the Trustees at regularly scheduled meetings, in connection with the review of the Fund’s investment management agreement.

In March 2021, the Trustees, among other things, discussed the memorandum provided by Fund counsel that summarized the legal standards and other considerations that are relevant to the Trustees in their deliberations regarding the renewal of the investment management agreement, and reviewed and discussed the qualifications of the investment management teams for the Fund, as well as the level of investment by the Fund’s portfolio managers in the Fund. In July 2021, the Trustees, among other things, reviewed the Fund’s management fees and total expense ratios, the financial statements of Amundi US and its parent companies, profitability analyses provided by Amundi US, and analyses from Amundi US as to possible economies of scale. The Trustees also reviewed the profitability of the institutional business of Amundi US as compared to that of Amundi US’s fund management business, and considered the differences between the fees and expenses of the Fund and the fees and expenses of Amundi US’s institutional accounts, as well as the different services provided by Amundi US to the Fund and to the institutional accounts. The Trustees further considered contract review materials, including additional materials received in response to the Trustees’ request, in September 2021.

At a meeting held on September 21, 2021, based on their evaluation of the information provided by Amundi US and third parties, the Trustees of the Fund, including the Independent Trustees voting separately, unanimously

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 49

approved the renewal of the investment management agreement for another year. In approving the renewal of the investment management agreement, the Trustees considered various factors that they determined were relevant, including the factors described below. The Trustees did not identify any single factor as the controlling factor in determining to approve the renewal of the agreement.

Nature, Extent and Quality of Services

The Trustees considered the nature, extent and quality of the services that had been provided by Amundi US to the Fund, taking into account the investment objective and strategy of the Fund. The Trustees also reviewed Amundi US’s investment approach for the Fund and its research process. The Trustees considered the resources of Amundi US and the personnel of Amundi US who provide investment management services to the Fund. They also reviewed the amount of non-Fund assets managed by the portfolio managers of the Fund. They considered the non-investment resources and personnel of Amundi US that are involved in Amundi US’s services to the Fund, including Amundi US’s compliance, risk management, and legal resources and personnel. The Trustees noted the substantial attention and high priority given by Amundi US’s senior management to the Pioneer Fund complex. The Trustees considered the effectiveness of Amundi US’s business continuity plan in response to the COVID-19 pandemic.

The Trustees considered that Amundi US supervises and monitors the performance of the Fund’s service providers and provides the Fund with personnel (including Fund officers) and other resources that are necessary for the Fund’s business management and operations. The Trustees also considered that, as administrator, Amundi US is responsible for the administration of the Fund’s business and other affairs. The Trustees considered Amundi US’s oversight of the process for transitioning custodian, transfer agent and sub-administration services to new service providers. The Trustees considered that the Fund reimburses Amundi US its pro rata share of Amundi US’s costs of providing administration services to the Pioneer Funds.

Based on these considerations, the Trustees concluded that the nature, extent and quality of services that had been provided by Amundi US to the Fund were satisfactory and consistent with the terms of the investment management agreement.

50 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

Performance of the Fund

In considering the Fund’s performance, the Trustees regularly review and discuss throughout the year data prepared by Amundi US and information comparing the Fund’s performance with the performance of its peer group of funds, as classified by Morningstar, Inc. (Morningstar), and with the performance of the Fund’s benchmark index. They also discuss the Fund’s performance with Amundi US on a regular basis. The Trustees’ regular reviews and discussions were factored into the Trustees’ deliberations concerning the renewal of the investment management agreement.

Management Fee and Expenses

The Trustees considered information showing the fees and expenses of the Fund in comparison to the management fees of its peer group of funds as classified by Morningstar and also to the expense ratios of a peer group of funds selected on the basis of criteria determined by the Independent Trustees for this purpose using data provided by Strategic Insight Mutual Fund Research and Consulting, LLC (Strategic Insight), an independent third party. The peer group comparisons referred to below are organized in quintiles. Each quintile represents one-fifth of the peer group. In all peer group comparisons referred to below, first quintile is most favorable to the Fund’s shareowners. The Trustees noted that they separately review and consider the impact of the Fund’s transfer agency and Fund- and Amundi US-paid expenses for sub-transfer agency and intermediary arrangements, and that the results of the most recent such review were considered in the consideration of the Fund’s expense ratio.

The Trustees considered that the Fund’s management fee for the most recent fiscal year was in the second quintile relative to the management fees paid by other funds in its Morningstar category for the comparable period. The Trustees considered that the expense ratio of the Fund’s Class Y shares for the most recent fiscal year was in the first quintile relative to its Strategic Insight peer group for the comparable period. The Trustees considered that the expense ratio of the Fund’s Class A shares for the most recent fiscal year was in the second quintile relative to its Strategic Insight peer group for the comparable period. The Trustees noted that Amundi US had agreed to waive fees and/or reimburse expenses in order to limit the ordinary operating expenses of the Fund.

The Trustees reviewed management fees charged by Amundi US to institutional and other clients, including publicly offered European funds sponsored by Amundi US’s affiliates, unaffiliated U.S. registered investment companies (in a sub-advisory capacity), and unaffiliated foreign and domestic separate accounts. The Trustees also considered Amundi US’s

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 51

costs in providing services to the Fund and Amundi US’s costs in providing services to the other clients and considered the differences in management fees and profit margins for fund and non-fund services. In evaluating the fees associated with Amundi US’s client accounts, the Trustees took into account the respective demands, resources and complexity associated with the Fund and other client accounts. The Trustees noted that, in some instances, the fee rates for those clients were lower than the management fee for the Fund and considered that, under the investment management and administration agreements with the Fund, Amundi US performs additional services for the Fund that it does not provide to those other clients or services that are broader in scope, including oversight of the Fund’s other service providers and activities related to compliance and the extensive regulatory and tax regimes to which the Fund is subject. The Trustees also considered the entrepreneurial risks associated with Amundi US’s management of the Fund.

The Trustees concluded that the management fee payable by the Fund to Amundi US was reasonable in relation to the nature and quality of the services provided by Amundi US.

Profitability

The Trustees considered information provided by Amundi US regarding the profitability of Amundi US with respect to the advisory services provided by Amundi US to the Fund, including the methodology used by Amundi US in allocating certain of its costs to the management of the Fund. The Trustees also considered Amundi US’s profit margin in connection with the overall operation of the Fund. They further reviewed the financial results, including the profit margins, realized by Amundi US from non-fund businesses. The Trustees considered Amundi US’s profit margins in comparison to the limited industry data available and noted that the profitability of any adviser was affected by numerous factors, including its organizational structure and method for allocating expenses. The Trustees concluded that Amundi US’s profitability with respect to the management of the Fund was not unreasonable.

Economies of Scale

The Trustees considered Amundi US’s views relating to economies of scale in connection with the Pioneer Funds as fund assets grow and the extent to which any such economies of scale are shared with the Fund and Fund shareholders. The Trustees recognize that economies of scale are difficult to identify and quantify, and that, among other factors that may be relevant, are the following: fee levels, expense subsidization, investment by Amundi US in research and analytical capabilities and Amundi US’s commitment and resource allocation to the Fund. The Trustees noted that profitability

52 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

also may be an indicator of the availability of any economies of scale, although profitability may vary for other reasons including due to reductions in expenses. The Trustees concluded that economies of scale, if any, were being appropriately shared with the Fund.

Other Benefits

The Trustees considered the other benefits that Amundi US enjoys from its relationship with the Fund. The Trustees considered the character and amount of fees paid or to be paid by the Fund, other than under the investment management agreement, for services provided by Amundi US and its affiliates. The Trustees further considered the revenues and profitability of Amundi US’s businesses other than the Fund business. To the extent applicable, the Trustees also considered the benefits to the Fund and to Amundi US and its affiliates from the use of “soft” commission dollars generated by the Fund to pay for research and brokerage services.

The Trustees considered that Amundi US is the principal U.S. asset management business of Amundi, which is one of the largest asset managers globally. Amundi’s worldwide asset management business manages over $2.12 trillion in assets (including the Pioneer Funds). The Trustees considered that Amundi US’s relationship with Amundi creates potential opportunities for Amundi US and Amundi that derive from Amundi US’s relationships with the Fund, including Amundi’s ability to market the services of Amundi US globally. The Trustees noted that Amundi US has access to additional research and portfolio management capabilities as a result of its relationship with Amundi and Amundi’s enhanced global presence that may contribute to an increase in the resources available to Amundi US. The Trustees considered that Amundi US and the Fund receive reciprocal intangible benefits from the relationship, including mutual brand recognition and, for the Fund, direct and indirect access to the resources of a large global asset manager. The Trustees concluded that any such benefits received by Amundi US as a result of its relationship with the Fund were reasonable.

Conclusion

After consideration of the factors described above as well as other factors, the Trustees, including the Independent Trustees, concluded that the investment management agreement for the Fund, including the fees payable thereunder, was fair and reasonable and voted to approve the proposed renewal of the investment management agreement.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 53

Trustees, Officers and Service Providers

Investment Adviser and Administrator
Amundi Asset Management US, Inc.

Custodian and Sub-Administrator
The Bank of New York Mellon Corporation

Independent Registered Public Accounting Firm
Ernst & Young LLP

Principal Underwriter
Amundi Distributor US, Inc.

Legal Counsel
Morgan, Lewis & Bockius LLP

Transfer Agent
BNY Mellon Investment Servicing (US) Inc.

Proxy Voting Policies and Procedures of the Fund are available without charge, upon request, by calling our toll free number (1-800-225-6292). Information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is publicly available to shareowners at www.amundi.com/us. This information is also available on the Securities and Exchange Commission’s web site at www.sec.gov.

54 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

This page was intentionally left blank.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 55

This page was intentionally left blank.

56 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

This page was intentionally left blank.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 57

This page was intentionally left blank.

58 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

This page was intentionally left blank.

Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22 59

This page was intentionally left blank.

60 Pioneer Global Sustainable Equity Fund | Semiannual Report | 2/28/22

How to Contact Amundi

We are pleased to offer a variety of convenient ways for you to contact us for assistance or information.

Write to us:

Amundi
P.O. Box 9897
Providence, R.I. 02940-8097

This report must be preceded or accompanied by a prospectus.

The Fund files a complete schedule of portfolio holdings with the Securities and Exchange Commission for the first and third quarters of each fiscal year as an exhibit to its reports on Form N-PORT. Shareholders may view the filed Form N-PORT by visiting the Commission’s web site at https://www.sec.gov.

Amundi Asset Management US, Inc.
60 State Street
Boston, MA 02109
www.amundi.com/us

Securities offered through Amundi Distributor US, Inc.,
60 State Street, Boston, MA 02109
Underwriter of Pioneer Mutual Funds, Member SIPC
© 2022 Amundi Asset Management US, Inc. 19129-16-0422

Pioneer High Income Municipal Fund

Semiannual Report | February 28, 2022

visit us: www.amundi.com/us

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 1

President’s Letter

Dear Shareholders,

For two years now, investors have faced unprecedented challenges, as the COVID-19 pandemic has not only dominated the headlines since March 2020, but has also led to significant changes in government and central-bank policies, both in the US and abroad, and affected the everyday lives of each of us. With 2022 now well underway, the situation, while improved, has continued to evolve.

Widespread distribution of the COVID-19 vaccines approved for emergency use in late 2020 led to a general decline in virus-related hospitalizations in the US and had a positive effect on overall market sentiment during most of the 2021 calendar year. The passage of two additional fiscal stimulus packages by US lawmakers in December 2020 and January 2021 also helped drive a strong market rally. Then, the late-2021 emergence of the highly infectious Omicron variant of the virus led to surges in cases and hospitalizations, especially outside of the US, but also in certain areas of this country. That development contributed to a slowdown in the global economic recovery, as some foreign governments reinstated strict virus-containment measures that had been relaxed after the rollout of the vaccines. Many of those renewed restrictions were lifted as case numbers again began to decline during the late-winter months, but it appears the possibility of further virus-containment measures could be with us for a while longer, given that occasional surges in new cases have continued to arise, particularly in non-US locations.

In the US, while performance of most asset classes, especially equities, was positive for the full 2021 calendar year, 2022, so far, has featured a less-friendly market environment, as volatility has remained high. Concerns over global supply chain issues, rising inflation, “hawkish” signals concerning less-accommodative future monetary policies from the Federal Reserve System (Fed), and partisan debates in Washington, DC over future spending and tax policies, are among the many factors that have led to greater uncertainty and an increase in market volatility. In addition, Russia's recent incursion into Ukraine has resulted in even greater market volatility, as economic sanctions placed on Russia by many Western countries have exacerbated the existing supply-chain issues and helped drive energy prices, including gas prices, to very high levels.

Despite those issues, and some of the recent difficulties that have affected the economy and the markets, we believe the distribution of the COVID-19 vaccines has provided a potential light at the end of the pandemic tunnel. With that said, the long-term impact on the global economy from COVID-19, while currently unknown, is likely to be considerable, as it is clear that several industries have already felt greater effects than others, and could continue to struggle for quite some time. Of course, geopolitical concerns, whether they are related to the conflict in Ukraine or other crises in different areas of the globe, can always have an effect on the markets, and so our investment teams will remain vigilant and continue to monitor the geopolitical landscape.

2 Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22

After leaving our offices in March of 2020 due to COVID-19, we have re-opened our US locations, but are maintaining all the necessary precautions, which at times may have us working more remotely than in person in order to ensure a safe working environment as new variants of the COVID-19 virus continue to arise and spread. I am proud of the careful planning that has taken place. Throughout the pandemic, our business has continued to operate without any disruption, and we all look forward to regaining a bit of normalcy after so many months of remote working.

Since 1928, Amundi US’s investment process has been built on a foundation of fundamental research and active management, principles which have guided our investment decisions for more than 90 years. We believe active management – that is, making active investment decisions – can help mitigate the risks during periods of market volatility.

At Amundi US, active management begins with our own fundamental, bottom-up research process. Our team of dedicated research analysts and portfolio managers analyzes each security under consideration, communicating directly with the management teams of the companies issuing the securities and working together to identify those securities that best meet our investment criteria for our family of funds. Our risk management approach begins with each and every security, as we strive to carefully understand the potential opportunity, while considering any and all risk factors.

Today, as investors, we have many options. It is our view that active management can serve shareholders well, not only when markets are thriving, but also during periods of market stress.

As you consider your long-term investment goals, we encourage you to work with your financial professional to develop an investment plan that paves the way for you to pursue both your short-term and long-term goals.

We greatly appreciate the trust you have placed in us and look forward to continuing to serve you in the future.

Sincerely,

Lisa M. Jones

Head of the Americas, President and CEO of US

Amundi Asset Management US, Inc.

April 2022

Any information in this shareowner report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 3

Portfolio Management Discussion | 2/28/22

In the following interview, Jonathan Chirunga and David Eurkus discuss the factors that influenced the performance of Pioneer High Income Municipal Fund* during the six-month period ended February 28, 2022. Mr. Chirunga, Managing Director, Director of High-Yield Municipals, and a portfolio manager at Amundi Asset Management US, Inc. (Amundi US), is responsible for the day-to-day management of the Fund, along with Mr. Eurkus, Managing Director, Director of Municipals, and a portfolio manager at Amundi US.

The second major factor affecting the performance of high-yield municipal bonds during the six-month period was Russia’s late-February invasion of Ukraine, which drove significant, across-the-board weakness

4 Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22

in the markets for higher-risk assets. Investors reacted not only to the mounting uncertainty stemming from the military conflict, but also to the potential for rising commodity prices, worsening supply-chain disruptions (already under stress due to COVID-19-related factors), and a further acceleration in the pace of inflation. The increased geopolitical uncertainty contributed to the worst sell-off in the high-yield municipal bond market since the COVID-19-driven downturn of early 2020.

On the positive side, fundamentals within the municipal bond market remained firm over the period. The combination of last year’s federal aid packages, the gradual reopening of the economy as the pandemic began to ease, and rising tax receipts, led to a steady improvement in the financial health of municipal issuers in general, and high-yield issuers in particular.

Security selection results within the special tax and housing sectors were particularly beneficial to the Fund’s relative performance during the period. (A special tax bond is a hybrid security that combines features of a general obligation bond and a  revenue bond. As a revenue bond, the special tax bond services its debt from special taxation funds. As a general obligation bond, it is secured by the  full faith and credit of the municipal issuer.)

Likewise, a portfolio overweight to tobacco bonds, which have been a key driver of the Fund’s relative returns over time, continued to aid results for the past six months. (Tobacco bonds are revenue bonds sold by certain states that are backed by annual payments to the government entities by tobacco companies in connection with the settlement of litigation claims.)

We have found tobacco bonds to be attractive investments, not only for their potential to enhance the Fund's performance, but also for the benefits received by the settling states that issue tobacco bonds since the establishment of the Master Settlement Agreement between the settling

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 5

states and the tobacco-related companies several years ago. Those benefits have included: substantial funding for the advancement of public health; the implementation of important tobacco-related public health measures; and funding towards establishment of a national foundation dedicated to significantly reducing the use of tobacco products among youths.

On the other hand, the Fund lost some benchmark-relative performance during the period due to holding underweight positions in many of the largest individual issuers within the high-yield municipal segment. Still, we believe it is more important to maintain diversification** within the portfolio, and to focus on the strongest individual issues, rather than taking excessive portfolio weightings in what we believe to be weaker credits for the purpose of gaining short-term relative performance. Along this same line, an underweight to Puerto Rico-issued bonds detracted from the Fund’s benchmark-relative returns for the period. We believe the Fund’s underweight positioning in Puerto Rico is appropriate, given the higher sensitivity of Puerto Rico’s issues to shifts in investors’ risk appetites, particularly in light of the uncertainty surrounding the Russia-Ukraine conflict.

With respect to individual holdings, a position in behavioral health center bonds issued by the Southwestern Illinois Development Authority was a key contributor to the Fund’s positive relative performance over the period. The Fund’s holdings in continuing care retirement center bonds issued by the Massachusetts State Development Financing Authority also aided relative returns. Conversely, senior living facility bonds issued by the New Hope Cultural Educational Facilities Financing Corporation (Texas), and tobacco settlement bonds issued by Suffolk County (New York), were among the key detractors from benchmark-relative results.

6 Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22

As has often been the case, headline news events have had a minimal effect on our day-to-day approach to managing the portfolio. Our goal is to invest the Fund in what we believe are fundamentally sound credits with attractive yields, while maintaining an appropriate level of portfolio diversification. We also seek to avoid experiencing defaults in the portfolio through our emphasis on fundamental research. That approach was successful over the past six months, as the Fund did not have any exposure to bonds that defaulted.

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 7

We believe this steady, long-term approach remains the most effective way to identify solid investment opportunities, and may help minimize the risk that comes with investing in the high-yield municipal market.

Please refer to the Schedule of Investments on pages 43–62 for a full listing of Fund securities.

All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility and heightened uncertainty. The market prices of securities may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, recessions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets, the spread of infectious illness or other public health issues, armed conflict including Russia's military invasion of Ukraine, sanctions against Russia, other nations or individuals or companies and possible countermeasures, or adverse investor sentiment. These conditions may continue, recur, worsen or spread.

Investments in high-yield or lower-rated securities are subject to greater-than-average price volatility, illiquidity and possibility of default.

When interest rates rise, the prices of fixed-income securities held by the Fund will generally fall. Conversely, when interest rates fall, the prices of fixed-income securities held by the Fund will generally rise.

Investments in the Fund are subject to possible loss due to the financial failure of issuers of underlying securities and their inability to meet their debt obligations.

The Fund’s investments, payment obligations and financing terms may be based on floating rates, such as LIBOR (London Interbank Offered Rate). Plans are underway to phase out the use of LIBOR. There remains uncertainty regarding the nature of any replacement rate and the impact of the transition from LIBOR on the Fund, issuers of instruments in which the Fund invests, and financial markets generally.

Prepayment risk is the chance that an issuer may exercise its right to prepay its security, if falling interest rates prompt the issuer to do so. Forced to reinvest the unanticipated proceeds at lower interest rates, the Fund would experience a decline in income and lose the opportunity for additional price appreciation.

The value of municipal securities can be adversely affected by changes in financial condition of municipal issuers, lower revenues, and regulatory and political developments.

8 Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22

The Fund may use derivatives, such as options, futures, inverse floating rate obligations, swaps, and others, which can be illiquid, may disproportionately increase losses, and have a potentially large impact on Fund performance. Derivatives may have a leveraging effect on the Fund.

A portion of income may be subject to local, state, federal, and/or alternative minimum tax. Capital gains, if any, are subject to a capital gains tax.

At times, the Fund’s investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors.

These risks may increase share price volatility.

Before investing, consider the product’s investment objectives, risks, charges and expenses. Contact your financial professional or Amundi Asset Management US, Inc., for a prospectus or summary prospectus containing this information. Read it carefully.

Any information in this shareholder report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is not a guarantee of future results.

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 9

Portfolio Summary | 2/28/22

† Amount rounds to less than 0.1%.

10 Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 11

Prices and Distributions | 2/28/22

Net Asset Value per Share

Index Definitions

The Bloomberg U.S. Municipal High Yield Bond Index is an unmanaged measure of the performance of the high-yield municipal bond market. Index returns are calculated monthly, assume reinvestment of dividends and, unlike Fund returns, do not reflect any fees, expenses or sales charges. It is not possible to invest directly in an index.

The index defined here pertains to the “Value of $10,000 Investment” and “Value of $5 Million Investment” charts shown on pages 13–15.

12 Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class A shares of Pioneer High Income Municipal Fund at public offering price during the periods shown, compared to that of the Bloomberg U.S. Municipal High Yield Bond Index.

Call 1-800-225-6292 or visit www.amundi.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

NAV results represent the percent change in net asset value per share. NAV returns would have been lower had sales charges been reflected. POP returns reflect deduction of maximum 4.50% sales charge. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

Pioneer High Income Municipal Fund | Semiannual Report | 2/28/22 13

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class C shares of Pioneer High Income Municipal Fund during the periods shown, compared to that of the Bloomberg U.S. Municipal High Yield Bond Index.