Exhibit 5.1

The Chrysler Building

405 Lexington Avenue, 26^th Floor

New York, New York 10174

Telephone: (212) 907-6457

Facsimile: (212) 208-4657

November 25, 2020

The Board of Directors

iBio, Inc.

8800 HSC Parkway

Bryan, Texas 77807-1107

Ladies and Gentlemen:

This opinion is furnished to you in connection with the filing of a Registration Statement on Form S-3 (the “Registration Statement”) on the date hereof by iBio, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), for the registration by the Company of up to $200,000,000 of any combination of the following securities of the Company:

The Common Stock, the Preferred Stock, the Debt Securities, the Warrants and the Units, plus any additional Common Stock, Preferred Stock, Debt Securities, Warrants and Units that may be registered pursuant to any registration statement that the Company may hereafter file with the Commission pursuant to Rule 462(b) under the Securities Act in connection with an offering by the Company pursuant to the Registration Statement, are collectively referred to herein as the “Securities.” The Securities are being registered for offer and sale from time to time pursuant to Rule 415 under the Securities Act.

We are acting as counsel for the Company in connection with the Registration Statement and the issuance and sale of the Securities thereunder. We are also acting as counsel for the Company in connection with the Controlled Equity Offering^SM Sales Agreement prospectus included in the Registration Statement (the “Sales Agreement ATM Prospectus”) relating to the issuance and sale of shares of Common Stock having an aggregate offering price of up to $100,000,000 (the “Sales Agreement Shares”) under the Sales Agreement, dated November 25, 2020, by and between the Company and Cantor Fitzgerald & Co. (the “Sales Agreement”).

In connection with this opinion, we have examined and relied upon originals, or copies certified to our satisfaction, of such records, documents, certificates, opinions, memoranda and other instruments as in our judgment are necessary or appropriate to enable us to render the opinion expressed below, including, but not limited to, signed copies of the Registration Statement to be filed with the Commission, including the exhibits thereto, the Sales Agreement, the Certificate of Incorporation of the Company (as amended or restated from time to time, the “Certificate of Incorporation”), the First Amended and Restated Bylaws of the Company (as amended or restated from time to time, the “Bylaws”) and resolutions of the Board of Directors of the Company provided to us by the Company. As to certain factual matters, we have relied upon a certificate of an officer of the Company and have not independently verified such matters.

In rendering this opinion, we have assumed the genuineness and authenticity of all signatures on original documents; the authenticity of all documents submitted to us as originals; the conformity to originals of all documents submitted to us as copies; the accuracy, completeness and authenticity of certificates of public officials; and the due authorization, execution and delivery of all documents where authorization, execution and delivery are prerequisites to the effectiveness of such documents.

With respect to our opinion as to the Common Stock (including the Sales Agreement Shares (as defined below)), we have assumed that, at the time of issuance and sale of any of the shares of Common Stock, a sufficient number of shares of Common Stock will be authorized and available for issuance and that the consideration for the issuance and sale of the shares of Common Stock (or Preferred Stock or Debt Securities convertible into, or Warrants exercisable for, Common Stock, or Common Stock included in a Unit) is in an amount that is not less than the par value of the Common Stock. In addition, we have also assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the Delaware General Corporation Law (the “DGCL”). With respect to our opinion as to the Preferred Stock, we have assumed that, at the time of issuance and sale, a sufficient number of shares of Preferred Stock is authorized, designated and available for issuance and that the consideration for the issuance and sale of the Preferred Stock (or Debt Securities convertible into, or Warrants exercisable for, Preferred Stock, or Preferred Stock included in a Unit) is in an amount that is not less than the par value of the Preferred Stock. We have also assumed that any Debt Securities, Warrants or Units offered under the Registration Statement, and the related Indenture, Warrant Agreement and Unit Agreement, respectively, will be executed in the forms filed as exhibits to the Registration Statement or incorporated by reference therein.

We have also assumed that (i) with respect to Securities issuable upon conversion of any convertible Preferred Stock, such convertible Preferred Stock will be duly authorized, validly issued, fully paid and non-assessable; and (ii) with respect to any Securities issuable upon conversion of any convertible Debt Securities, upon exercise of any Warrants or as part of a Unit, such convertible Debt Securities, Warrants or Units will constitute valid and legally binding obligations of the Company, enforceable against the Company in accordance with their terms, except as enforcement may be limited by applicable bankruptcy, insolvency, reorganization, arrangement, moratorium or other similar laws affecting creditors’ rights, and subject to general equity principles and to limitations on availability of equitable relief, including specific performance. We have also assumed that any Units issued by the Company pursuant to the Registration Statement, the Prospectus and the related Prospectus Supplement may be issued pursuant to a valid, binding, and enforceable Unit Agreement between the Company and a bank or trust company as the Unit Agent. We have also assumed that any Indenture, Warrant Agreement and Unit Agreement will be governed by and construed in accordance with the laws of the State of New York.

With respect to the Sales Agreement Shares, we have assumed (i) that the specific sale of the Sales Agreement Shares will be duly authorized by the Board of Directors of the Company, a duly authorized committee thereof or a person or body pursuant to an authorization granted in accordance with Section 152 of the DGCL and (ii) that the Sales Agreement Shares will be issued for a price per share equal to or greater than the minimum price authorized by the Board of Directors of the Company or a duly authorized committee thereof or a person or body pursuant to an authorization granted prior to the date hereof (the “Minimum Price”) and that no event occurs that causes the number of authorized shares of Common Stock available for issuance by the Company to be less than the number of then unissued shares of Common Stock that may be issued for the Minimum Price.  With respect to the Sales Agreement Shares, we express no opinion to the extent that future issuances of securities of the Company and/or anti-dilution adjustments to outstanding securities of the Company cause the number of shares of Common Stock authorized less the sum of the number of shares outstanding or committed to be issued to exceed the number of Sales Agreement Shares then issuable under the Sales Agreement.

On the basis of the foregoing and in reliance thereon, and subject to the qualifications herein stated, we are of the opinion that:

Our opinions herein are expressed solely with respect to the DGCL and, as to the Debt Securities, the Warrants and the Units constituting valid and legally binding obligations of the Company, the laws of the State of New York. Our opinion is based on these laws as in effect on the date hereof. We express no opinion to the extent that any other laws are applicable to the subject matter hereof and express no opinion and provide no assurance as to compliance with any federal or state securities law, rule or regulation.

We are members of the Bar of the State of New York and the foregoing opinion is limited to the laws of the State of New York and the General Corporation Law of the State of Delaware.

We hereby consent to the filing of this opinion with the Commission as an exhibit to the Registration Statement in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act and to the use of our name therein and in the related Prospectus and the Sales Agreement ATM Prospectus under the caption “Legal Matters.” We further consent to the incorporation by reference of this opinion into any registration statement filed pursuant to Rule 462(b) under the Securities Act with respect to additional Securities. In giving such consent, we do not hereby 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.