Exhibit 5.1

SIMPSON THACHER & BARTLETT LLP

425 LEXINGTON AVENUE

NEW YORK, NY 10017-3954

TELEPHONE: +1-212-455-2000

FACSIMILE: +1-212-455-2502

Apria, Inc.

7353 Company Drive

Indianapolis, Indiana 46237

Ladies and Gentlemen:

We have acted as counsel to Apria, Inc., a Delaware corporation (the “Company”), in connection with the Registration Statement on Form S-1 (File No. 333-252146) (as amended, the “Registration Statement”) filed by the Company with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Act”), relating to the sale by the selling stockholders identified in the Registration Statement (the “Selling Stockholders”) of an aggregate of 8,625,000 shares of common stock, par value $0.01 per share (“Common Stock”) to be issued to the Selling Stockholders pursuant to certain reorganization transactions to be completed prior to the offering (together with any additional shares of Common Stock that may be sold by the Selling Stockholders pursuant to Rule 462(b) (as prescribed by the Commission pursuant to the Act) in connection with the offering described in the Registration Statement, the “Shares”).

BEIJING         HONG KONG         HOUSTON         LONDON         LOS ANGELES         PALO ALTO         SÃO PAULO         TOKYO        WASHINGTON, D.C.

We have examined the Registration Statement, a form of the Amended and Restated Certificate of Incorporation of the Company (the “Amended Certificate”), which has been filed with the Commission as an exhibit to the Registration Statement and a form of the Master Reorganization Agreement among the Company, Apria Healthcare Group Inc. and the other parties thereto (the “Master Reorganization Agreement”). In addition, we have examined, and have relied as to matters of fact upon, originals, or duplicates or certified or conformed copies, of such records, agreements, documents and other instruments and such certificates or comparable documents of public officials and of officers and representatives of the Company and have made such other investigations as we have deemed relevant and necessary in connection with the opinions hereinafter set forth.

In rendering the opinion set forth below, we have assumed the genuineness of all signatures, the legal capacity of natural persons, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as duplicates or certified or conformed copies and the authenticity of the originals of such latter documents.

Based upon the foregoing, and subject to the qualifications, assumptions and limitations stated herein, we are of the opinion that (1) when the Board of Directors of the Company (the “Board”) has taken all necessary corporate action to authorize and approve the issuance of the Shares in accordance with the terms of the Master Reorganization Agreement, (2) when the Amended Certificate has been duly filed with the Secretary of State of Delaware and (3) upon payment and delivery in accordance with the Master Reorganization Agreement approved and adopted by the Board, the Shares will be validly issued, fully paid and nonassessable.

We do not express any opinion herein concerning any law other than the Delaware General Corporation Law.

We hereby consent to the filing of this opinion letter as Exhibit 5.1 to the Registration Statement and to the use of our name under the caption “Legal Matters” in the prospectus included in the Registration Statement.