Exhibit 5.1

Baker & McKenzie LLP 452 Fifth Avenue
New York, NY 10018
United States   Tel: +1 212 626 4100 Fax: +1 212 310 1600 www.bakermckenzie.com

September 8, 2020 Celsion Corporation 997 Lenox Drive, Suite 100
Lawrenceville, NJ 08648 Ladies and Gentlemen: We have acted as special counsel for Celsion Corporation, a Delaware corporation (the “Company”), in connection with the sale of shares of the Company’s common stock (the “Shares”) pursuant to that certain Purchase Agreement, dated September 8, 2020 executed by the Company and Lincoln Park Capital Fund, LLC (the “Agreement”). The Shares are registered pursuant to the Company’s Registration Statement on Form S-3 (Registration Number 333-227236), as amended through the date hereof (the “Registration Statement”), which was declared effective by the Securities and Exchange Commission (the “SEC”) on October 12, 2018. We have reviewed an executed copy of the Agreement, and we have examined the originals, or photostatic or certified copies, of such records of the Company, of certificates of officers of the Company and of public documents, and such other documents as we have deemed relevant and necessary as the basis of the opinions set forth below. In such examination, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as photostatic or certified copies and the authenticity of the originals of such copies. Based upon and subject to the foregoing, we are of the opinion that the Shares have been duly and validly authorized and, when issued in accordance with the terms of the Agreement, will be validly issued, fully paid and non-assessable. The opinion expressed above is limited to the laws of the State of New York, the General Corporation Law of the State of Delaware, and the federal laws of the United States of America. This opinion letter is limited to the matters stated herein, and no opinion is implied or may be inferred beyond the matters expressly stated. We hereby consent to the use of our opinion as herein set forth as an exhibit to the Registration Statement and to the use of our name under the caption “Legal Matters” in the prospectus forming a part of the Registration Statement. In giving this consent, we do not hereby admit that we come within the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the SEC promulgated thereunder or Item 509 of Regulation S-K.

Very truly yours,

/s/ Baker & Mckenzie LLP

BAKER & McKENZIE LLP

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