ONEOK (OKE) 8-KONEOK Announces $750 Million Notes Offering

Exhibit 5.1

		301 Congress Avenue, Suite 900 Austin, TX 78701 Tel: +1.737.910.7300 Fax: +1.737.910.7301 www.lw.com   FIRM / AFFILIATE OFFICES
November 18, 2022		Austin     Beijing     Boston     Brussels     Century City     Chicago     Dubai     Düsseldorf     Frankfurt     Hamburg     Hong Kong     Houston     London     Los Angeles     Madrid		Milan Munich New York Orange County Paris Riyadh San Diego San Francisco Seoul Shanghai Silicon Valley Singapore Tel Aviv Tokyo Washington, D.C.

ONEOK, Inc.

100 West Fifth Street

Tulsa, Oklahoma 74103

Re: Registration Statement No. 333-239348

Ladies and Gentlemen:

We have acted as special counsel to ONEOK, Inc., an Oklahoma corporation (the “Company”), ONEOK Partners, L.P., a Delaware limited partnership (“ONEOK Partners”), and ONEOK Partners Intermediate Limited Partnership, a Delaware limited partnership (“ONEOK Partners Intermediate” and, together with ONEOK Partners, the “Guarantors”), in connection with the issuance by the Company of $750 million aggregate principal amount of its 6.100% Senior Notes due 2032 (the “Notes”) and, the guarantee of the Notes (the “Guarantee” and, together with the Notes, the “Securities”) by the Guarantors, under the Base Indenture dated as of January 26, 2012, as amended and supplemented (the “Base Indenture”), by and among the Company and U.S. Bank Trust Company, National Association (successor in interest to U.S. Bank National Association), as trustee, as further supplemented by the Nineteenth Supplemental Indenture, dated as of November 18, 2022 (the “Supplemental Indenture” and the Base Indenture as so supplemented, the “Indenture”), and pursuant to a registration statement on Form S-3 under the Securities Act of 1933, as amended (the “Act”), filed with the Securities and Exchange Commission (the “Commission”) on June 22, 2020 (Registration No. 333-239348) (as so filed, the “Registration Statement”). This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or related prospectus, other than as expressly stated herein with respect to the issuance of the Securities.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company, the general partners of each of the Guarantors and others as to factual matters without having independently verified such factual matters. We are opining herein as to the internal laws of the State of New York and the Delaware Revised Uniform Limited Partnership Act, and we express no opinion with respect to the applicability thereto, or the effect thereon, of the laws of any other jurisdiction or, in the case of Delaware, any other laws, or as to any matters of municipal law or the laws of any local agencies within any state.

November 18, 2022

Page 2

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof, when the Securities have been duly executed, issued, and authenticated in accordance with the terms of the Indenture and delivered against payment therefor in the circumstances contemplated by the underwriting agreement, dated November 15, 2022, among the Company, the Guarantors and Barclays Capital Inc., Mizuho Securities USA LLC, TD Securities (USA) LLC and Wells Fargo Securities, LLC, as representatives of the several underwriters named therein, the Securities will have been duly authorized by all necessary limited partnership action of the Guarantors, and will be legally valid and binding obligations of the Guarantors, enforceable against the Company and the Guarantors in accordance with their terms.

Our opinion is subject to:

November 18, 2022

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With your consent, we have assumed (a) that the Indenture and the Securities (collectively, the “Documents”) have been duly authorized, executed and delivered by the parties thereto other than the Guarantors, (b) that the Documents constitute legally valid and binding obligations of the parties thereto other than the Guarantors, enforceable against each of them in accordance with their respective terms, and (c) that the status of the Documents as legally valid and binding obligations of the parties is not affected by any (i) breaches of, or defaults under, agreements or instruments, (ii) violations of statutes, rules, regulations or court or governmental orders, or (iii) failures to obtain required consents, approvals or authorizations from, or make required registrations, declarations or filings with, governmental authorities.

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Company’s Form 8-K dated November 18, 2022 and to the reference to our firm contained in the Prospectus under the heading “Legal.” In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.