Exhibit 5.1

[Fox Rothschild LLP Letterhead]

March 1, 2024

Inogen, Inc.

859 Ward Drive

Goleta, California 93111

Re: Inogen, Inc.

Registration Statement on Form S‑8

Ladies and Gentlemen:

We have acted as counsel to Inogen, Inc., a Delaware corporation (the “Company”), in connection with the preparation and filing with the Securities and Exchange Commission (the “Commission”) of the Company’s Registration Statement on Form S-8 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Securities Act”), registering the offer and sale of up to 225,000 shares of the Company’s Common Stock, par value $0.001 per share (the “Shares”), issuable upon (i) the vesting of a maximum of 75,000 time-based restricted stock units granted to Michael Bourque, appointed to serve as the Company’s Executive Vice President, Chief Financial Officer and Treasurer, pursuant to an Inducement Award Restricted Stock Unit Agreement – Time-Based, and (ii) the vesting of a maximum of 150,000 shares of performance-based restricted stock units granted to Mr. Bourque pursuant to an Inducement Award Restricted Stock Unit Agreement – Performance-Based, each granted to Mr. Bourque to induce Mr. Bourque to accept employment with the Company in accordance with Nasdaq Listing Rule 5635(c)(4) (collectively, the “Inducement Award Agreements”).

In connection with this opinion, we have examined and relied upon the originals, or copies certified or otherwise identified to our satisfaction, of such records, documents, certificates and other instruments as in our judgment are necessary or appropriate to enable us to render the opinions expressed below. As to certain factual matters, we have relied upon certificates of the officers of the Company and have not sought to independently verify such matters.

In rendering this opinion, we have assumed the genuineness and authenticity of all signatures on original documents; the legal capacity of all natural persons; the authenticity of all documents submitted to us as originals; the conformity to originals of all documents submitted to us as certified or photocopies; the authenticity of the originals of such latter documents, including electronic signatures made and/or transmitted using electronic signature technology (e.g., via DocuSign or similar electronic signature technology); that any such signed electronic record shall be valid and as effective to bind the party so signing as a paper copy bearing such party’s handwritten signature; the accuracy and completeness of all documents and records reviewed by us; the accuracy, completeness and authenticity of certificates issued by any governmental official, office or agency and the absence of change in the information contained therein from the effective date of any such certificate; and other than for the Company, the due authorization, execution and delivery of all documents where authorization, execution and delivery are prerequisites to the effectiveness of such documents.

Our opinion herein is expressed solely with respect to 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) and is based on these laws as in effect on the date hereof. We express no opinion as to whether the laws of any jurisdiction are applicable to the subject matter hereof. We are not rendering any opinion as to compliance with any federal or other state law, rule or regulation relating to securities, or to the sale or issuance thereof.

On the basis of the foregoing and in reliance thereon, and subject to the qualifications herein stated, we are of the opinion that the Shares registered pursuant to the Registration Statement have been duly and validly authorized and reserved for issuance and that upon the issuance of the Shares and payment therefor in accordance with the provisions of the Inducement Award Agreements, the Shares will be validly issued, fully paid and non-assessable.

We hereby consent to the filing of this opinion as an exhibit to the Registration Statement. In giving such consent, we do not 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 SEC thereunder. This opinion is expressed as of the date hereof, and we disclaim any undertaking to update or supplement this opinion or to advise you of any subsequent changes in the facts stated or assumed herein or of any subsequent changes in applicable law.

Very truly yours,

/s/ Fox Rothschild LLP

FOX ROTHSCHILD LLP