EX-5.1

Exhibit 5.1

May 17, 2023

Emergent BioSolutions Inc.

400 Professional Drive, Suite 400

Gaithersburg, Maryland 20879

Ladies and Gentlemen:

We have acted as counsel to Emergent BioSolutions Inc., a Delaware corporation (the “Company”), in connection with the registration by the Company under the Securities Act of 1933, as amended (the “Securities Act”), of the offer and sale of shares of the Company’s common stock, par value $0.001 per share, having an aggregate offering price of up to $150,000,000 (the “Shares”), pursuant to the Equity Distribution Agreement, dated May 17, 2023, among the Company and Evercore Group L.L.C. and RBC Capital Markets, LLC, as sales agents (the “Distribution Agreement”). The offer and sale of the Shares are being registered under the Securities Act pursuant to the Company’s Registration Statement on Form S-3 (File No. 333-258634), which was filed with the Securities and Exchange Commission on August 9, 2021 (such registration statement is herein referred to as the “Registration Statement”).

We have reviewed the Distribution Agreement, the Registration Statement and the prospectus, dated August 9, 2021, as supplemented by a prospectus supplement dated May 17, 2023, with respect to the offer and sale of the Shares, as filed with the Securities and Exchange Commission on May 17, 2023. We have also reviewed such corporate records, certificates and other documents, and such questions of law, as we have considered necessary or appropriate for the purposes of this opinion.

We have assumed that all signatures are genuine, that all documents submitted to us as originals are authentic and that all copies of documents submitted to us conform to the originals.

We have relied as to certain matters on information obtained from public officials, officers of the Company and other sources believed by us to be responsible.

Based upon the foregoing, we are of the opinion that the Shares have been duly authorized, and when issued and sold by the Company pursuant to the terms of the Distribution Agreement and upon receipt by the Company of full payment therefor in accordance with the Distribution Agreement, will be validly issued, fully paid and non-assessable.

We are members of the bar of the District of Columbia. We do not express any opinion herein on any laws other than the Delaware General Corporation Law.