Exhibit 5.1

2727 NORTH HARWOOD STREET • DALLAS, TEXAS 75201.1515

TELEPHONE: +1.214.220.3939 • JONESDAY.COM

May 24, 2022

Lennox International Inc.

2140 Lake Park Boulevard

Richardson, Texas 75080

Re: Registration Statement on Form S-8 Filed by Lennox International Inc.

Ladies and Gentlemen:

We have acted as counsel for Lennox International Inc., a Delaware corporation (the “Company”), in connection with the registration under the Securities Act of 1933 (the “Act”) of 1,000,000 shares (the “Shares”) of the Company’s common stock, par value $.01 per share, that may be issued or delivered and sold pursuant to the Lennox International Inc. 2022 Employee Stock Purchase Plan (the “Plan”). In connection with the opinion expressed herein, we have examined such documents, records and matters of law as we have deemed relevant or necessary for purposes of such opinion. Based on the foregoing, and subject to the further limitations, qualifications and assumptions set forth herein, we are of the opinion that the Shares that may be issued or delivered and sold pursuant to the Plan have been authorized by all necessary corporate action of the Company and, when issued or delivered and sold in accordance with the terms of the Plan against payment of consideration therefor as provided therein, will be validly issued, fully paid and nonassessable, provided that the consideration for the Shares is at least equal to the stated par value thereof.

The opinion expressed herein is limited to the General Corporation Law of the State of Delaware, as currently in effect, and we express no opinion with respect to any other law of the State of Delaware or the laws of any other jurisdiction. In addition, we have assumed that the resolutions authorizing the Company to issue or deliver and sell the Shares pursuant to the Plan will be in full force and effect at all times at which such Shares are issued or delivered or sold by the Company, and that the Company will take no action inconsistent with such resolutions.

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement on Form S-8 filed by the Company to effect the registration of the Shares to be issued or delivered and sold pursuant to the Plan under the Act. In giving such consent, we do not thereby admit that we are included in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission promulgated thereunder.

Very truly yours,

/s/ Jones Day