EXHIBIT 5.1

	lawyers@saul.com   www.saul.com
	June 26, 2020

Supernus Pharmaceuticals, Inc.

9715 Key West Avenue

Rockville, Maryland 20850

The Board of Directors:

We refer to the Registration Statement on Form S-8 (the “Registration Statement”) of Supernus Pharmaceuticals, Inc., a Delaware corporation (the “Company”), to be filed with the Securities and Exchange Commission covering the registration under the Securities Act of 1933, as amended (the “Securities Act”), of 4,000,000 shares of common stock, par value $0.001 per share, of the Company (the “Shares”) authorized pursuant to the Fourth Amended and Restated 2012 Equity Incentive Plan and the Third Amended and Restated 2012 Employee Stock Purchase Plan (hereinafter referred to collectively as the (“Plans”).

We have examined the Registration Statement, the Certificate of Incorporation and By-Laws of the Company and such records, certificates and other documents as we have considered necessary or appropriate for the purposes of this Opinion.

Based upon and subject to the foregoing, we are of the opinion that the Shares to be issued pursuant to the terms of the Plans have been duly authorized and, when issued in accordance with the terms of the Plans, will be duly and validly issued, fully paid and non-assessable.

We hereby consent to the use of our name in the Registration Statement as counsel who will pass upon the legality of the Shares for the Company and as having prepared this Opinion as an exhibit to the Registration Statement. In giving the foregoing consent, we do not thereby 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 Securities and Exchange Commission thereunder.