Exhibit 5.1

300 North LaSalle

Chicago, Illinois 60654

(312) 862-2000   www.kirkland.com Facsimile: (312) 862-2200

May 9, 2018

Tenneco Inc.

500 North Field Drive

Lake Forest, Illinois 60045

Ladies and Gentlemen:

We are acting as special counsel to Tenneco Inc., a Delaware corporation (the “Company”), in connection with the preparation of the Registration Statement on Form S-3 (such Registration Statement, as amended or supplemented, is hereinafter referred to as the “Registration Statement”) filed by the Company with the Securities and Exchange Commission (the “Commission”) on May 9, 2018 under the Securities Act of 1933, as amended (the “Securities Act”). The Registration Statement relates to the issuance and sale from time to time, pursuant to Rule 415 of the General Rules and Regulations promulgated under the Securities Act, of an unspecified amount of common stock of the Company, par value $0.01 per share (the “Common Stock”), in one or more offerings from time to time on a delayed or continuous basis.

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 for the purposes of this opinion, including (i) the organizational documents of the Company, including the Restated Certificate of Incorporation as certified by the Secretary of State of the State of Delaware on May 7, 2018, (ii) minutes and records of the corporate proceedings of the Company and (iii) the Registration Statement and the exhibits thereto.

For purposes of this opinion, we have assumed the authenticity of all documents submitted to us as originals, the conformity to the originals of all documents submitted to us as copies and the authenticity of the originals of all documents submitted to us as copies. We have also assumed the legal capacity of all natural persons, the genuineness of the signatures of persons signing all documents in connection with which this opinion is rendered, the authority of such persons signing on behalf of the parties thereto other than the Company and the due authorization, execution and delivery of all documents by the parties thereto other than the Company. We have not independently established or verified any facts relevant to the opinion expressed herein, but have relied upon statements and representations of officers and other representatives of the Company and others.

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Tenneco Inc.

May 9, 2018

Page 2

We have also assumed that:

(i) the Registration Statement and any amendments thereto (including post-effective amendments) will be effective and will comply with all applicable laws at the time the Common Stock is offered or issued as contemplated by the Registration Statement;

(ii) a prospectus supplement or term sheet (“Prospectus Supplement”) will have been prepared and filed with the Commission describing the Common Stock offered thereby and will comply with all applicable laws;

(iii) all Common Stock will be issued and sold in compliance with applicable federal and state securities laws and in the manner stated in the Registration Statement and the appropriate Prospectus Supplement;

(iv) the Company will have obtained any legally required consents, approvals, authorizations and other orders of the Commission and any other regulatory authorities necessary to issue and sell the Common Stock being offered; and

(v) a definitive underwriting, purchase, sales agent or similar agreement (each, an “Underwriting Agreement”) with respect to any Common Stock offered or issued will have been duly authorized and validly executed and delivered by the Company and the other parties thereto.

Based upon and subject to the foregoing qualifications, assumptions and limitations and the further limitations set forth below, we are of the opinion that the shares of Common Stock to be issued and sold by the Company, when duly authorized by appropriate corporate action of the Company (including the Board of Directors of the Company or a committee thereof), and issued, sold and delivered against payment therefor in accordance with such authorization, the applicable Underwriting Agreement and applicable law and in the manner and for the consideration stated in the Registration Statement and the applicable Prospectus Supplement, will be validly issued, fully paid and non-assessable.

Our opinion expressed above is subject to the qualification that we express no opinion as to the applicability of, compliance with, or effect of any laws except the General Corporation Law of the State of Delaware (including the statutory provisions, all applicable provisions of the Delaware constitution and reported judicial decisions interpreting the foregoing).

We hereby consent to the filing of this opinion with the Commission as Exhibit 5.1 to the Registration Statement. We also consent to the reference to our firm under the heading “Legal Matters” in the Registration Statement. In giving this consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

Tenneco Inc.

May 9, 2018

Page 3

We do not find it necessary for the purposes of this opinion, and accordingly we do not purport to cover herein, the application of the securities or “Blue Sky” laws of the various states to the issuance and sale of the Common Stock.

This opinion is limited to the specific issues addressed herein, and no opinion may be inferred or implied beyond that expressly stated herein. We assume no obligation to revise or supplement this opinion after the date of effectiveness should the General Corporation Law of the State of Delaware be changed by legislative action, judicial decision or otherwise after the date hereof.

This opinion is furnished to you in connection with the filing of the Registration Statement in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.

Very truly yours,

/s/ Kirkland & Ellis LLP

KIRKLAND & ELLIS LLP