Cyrus King (September 6, 1772 – April 25, 1817) was a U.S. Representative from Massachusetts, half-brother of Rufus King.

Born in Scarborough in Massachusetts Bay's Province of Maine, King attended Phillips Academy, Andover, Massachusetts, and was graduated from Columbia College, New York City, in 1794. He studied law.

King served as private secretary to Rufus King when he was United States Minister to England in 1796. He completed law studies in Biddeford and was admitted to the bar in 1797, commencing his law practice in Saco. He served as major general of the Sixth Division, Massachusetts Militia. King was one of the founders of Thornton Academy in Saco.

King was elected as a Federalist to the Thirteenth and Fourteenth Congresses (March 4, 1813 – March 3, 1817).

He returned to Saco (then in Massachusetts' District of Maine), where he died on April 25, 1817, and was interred in Laurel Hill Cemetery.

• United States Congress. "Cyrus King (id: K000197)". Biographical Directory of the United States Congress.

 This article incorporates public domain material from the Biographical Directory of the United States Congress

• Finding aid to Cyrus King papers at Columbia University. Rare Book & Manuscript Library.