Exhibit 5.1

CRAVATH, SWAINE & MOORE LLP

		WORLDWIDE PLAZA
JOHN W. WHITE EVAN R. CHESLER RICHARD W. CLARY STEPHEN L. GORDON ROBERT H. BARON DAVID MERCADO CHRISTINE A. VARNEY PETER T. BARBUR THOMAS G. RAFFERTY MICHAEL S. GOLDMAN RICHARD HALL JULIE A. NORTH ANDREW W. NEEDHAM STEPHEN L. BURNS KATHERINE B. FORREST KEITH R. HUMMEL DAVID J. KAPPOS DANIEL SLIFKIN ROBERT I. TOWNSEND, III WILLIAM J. WHELAN, III PHILIP J. BOECKMAN WILLIAM V. FOGG FAIZA J. SAEED RICHARD J. STARK	THOMAS E. DUNN MARK I. GREENE DAVID R. MARRIOTT MICHAEL A. PASKIN ANDREW J. PITTS MICHAEL T. REYNOLDS ANTONY L. RYAN GEORGE E. ZOBITZ GEORGE A. STEPHANAKIS DARIN P. MCATEE GARY A. BORNSTEIN TIMOTHY G. CAMERON KARIN A. DEMASI DAVID S. FINKELSTEIN DAVID GREENWALD RACHEL G. SKAISTIS PAUL H. ZUMBRO ERIC W. HILFERS GEORGE F. SCHOEN ERIK R. TAVZEL CRAIG F. ARCELLA DAMIEN R. ZOUBEK LAUREN ANGELILLI TATIANA LAPUSHCHIK	825 EIGHTH AVENUE NEW YORK, NY 10019-7475 TELEPHONE: +1-212-474-1000 FACSIMILE: +1-212-474-3700 CITYPOINT ONE ROPEMAKER STREET LONDON EC2Y 9HR TELEPHONE: +44-20-7453-1000 FACSIMILE: +44-20-7860-1150	ALYSSA K. CAPLES JENNIFER S. CONWAY MINH VAN NGO KEVIN J. ORSINI MATTHEW MORREALE JOHN D. BURETTA J. WESLEY EARNHARDT YONATAN EVEN BENJAMIN GRUENSTEIN JOSEPH O. ZAVAGLIA STEPHEN M. KESSING LAUREN A. MOSKOWITZ DAVID J. PERKINS JOHNNY G. SKUMPIJA J. LEONARD TETI, II D. SCOTT BENNETT TING S. CHEN CHRISTOPHER K. FARGO KENNETH C. HALCOM DAVID M. STUART AARON M. GRUBER O. KEITH HALLAM, III OMID H. NASAB DAMARIS HERNÁNDEZ	JONATHAN J. KATZ MARGARET SEGALL D’AMICO RORY A. LERARIS KARA L. MUNGOVAN NICHOLAS A. DORSEY ANDREW C. ELKEN JENNY HOCHENBERG VANESSA A. LAVELY G.J. LIGELIS JR. MICHAEL E. MARIANI LAUREN R. KENNEDY SASHA ROSENTHAL-LARREA ALLISON M. WEIN SPECIAL COUNSEL SAMUEL C. BUTLER OF COUNSEL MICHAEL L. SCHLER

June 14, 2019

Parker-Hannifin Corporation

$575,000,000 2.700% Senior Notes due 2024

$1,000,000,000 3.250% Senior Notes due 2029

$800,000,000 4.000% Senior Notes due 2049

Ladies and Gentlemen:

We have acted as counsel for Parker-Hannifin Corporation, an Ohio corporation (the “Company”), in connection with the public offering and sale by the Company of $575,000,000 aggregate principal amount of 2.700% Senior Notes due 2024 (the “2024 Notes”), $1,000,000,000 aggregate principal amount of 3.250% Senior Notes due 2029 (the “2029 Notes”) and $800,000,000 aggregate principal amount of 4.000% Senior Notes due 2049 (the “2049 Notes” and, together with the 2024 Notes and the 2029 Notes, the “Notes”), to be issued under the indenture dated as of May 3, 1996 (the “Base Indenture”), between the Company and Wells Fargo Bank, N.A. (as successor trustee to National City Bank), as trustee (the “Trustee”), and the Officers’ Certificates of the Company dated as of June 14, 2019, establishing the terms of the Notes (the “Officers’ Certificates” and, together with the Base Indenture, the “Indenture”).

In that connection, we have examined originals, or copies certified or otherwise identified to our satisfaction, of such documents, corporate records and other instruments as we have deemed necessary or appropriate for the purposes of this opinion, including (a) the Indenture and the form of Note contained therein and (b) the Registration Statement on Form S-3 (Registration No. 333-214864) filed with the Securities and Exchange Commission (the “Commission”) on December 1, 2016 (the “Registration Statement”), with respect to registration under the Securities Act of 1933, as amended (the “Securities Act”) of an unlimited aggregate amount of various securities of the Company, to be issued from time to time by the Company.

In rendering this opinion, we have assumed, with your consent and without independent investigation or verification, the genuineness of all signatures, the legal capacity and competency of all natural persons, the authenticity of all documents submitted to us as originals and the

conformity to authentic original documents of all documents submitted to us as duplicates or copies. We also have assumed, with your consent, that the Indenture has been duly authorized, executed and delivered by, and represents a legal, valid and binding obligation of, the Trustee and that the form of the Notes will conform to that included in the Indenture.

Based on the foregoing and subject to the qualifications set forth herein, we are of opinion as follows:

1.    Assuming that the Indenture has been duly authorized, executed and delivered by the Company, the Indenture constitutes a legal, valid and binding obligation of the Company, enforceable against the Company in accordance with its terms (subject to applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent transfer and other similar laws affecting creditors’ rights generally from time to time in effect and to general principles of equity, including, without limitation, concepts of materiality, reasonableness, good faith and fair dealing, regardless of whether considered in a proceeding in equity or at law).

2.    Assuming that the Notes have been duly authorized by the Company, the Notes, when executed and authenticated in accordance with the provisions of the Indenture and delivered and paid for as contemplated in the Registration Statement, will constitute legal, valid and binding obligations of the Company, entitled to the benefits of the Indenture and enforceable against the Company in accordance with their terms (subject to applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent transfer and other similar laws affecting creditors’ rights generally from time to time in effect and to general principles of equity, including, without limitation, concepts of materiality, reasonableness, good faith and fair dealing, regardless of whether considered in a proceeding in equity or at law).

We are admitted to practice in the State of New York, and we express no opinion as to matters governed by any laws other than the laws of the State of New York. In particular, we do not purport to pass on any matter governed by the laws of the State of Ohio. For purposes of our opinion, we have assumed that (i) the Company has been duly incorporated and is a validly existing corporation under the laws of the State of Ohio and (ii) the Indenture and the Notes have been duly authorized, executed and delivered by the Company. With respect to all matters of the laws of the State of Ohio, we note that you are being provided with the opinion, dated the date hereof, of Joseph Leonti, Vice President, General Counsel and Secretary of the Company.

2

We hereby consent to the filing of this opinion with the Commission as Exhibit 5.1 to the Current Report on Form 8-K dated the date hereof and incorporated by reference into the Registration Statement. We also consent to the reference to our firm under the caption “Legal Matters” in the Prospectus Supplement constituting part of the Registration Statement. In giving this consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission promulgated thereunder.

Very truly yours,

/s/ Cravath, Swaine & Moore LLP

Parker-Hannifin Corporation

6035 Parkland Boulevard

Cleveland, OH 44124-4141

3