Thomas Clarke Theaker (February 4, 1812 – July 16, 1883) was an American politician who served one term as U.S.

He also served as commissioner of the United States Patent Office from 1865 to 1868.

Theaker was a native of York, Pennsylvania, but moved to Bridgeport, Ohio, in 1830, where he became a wheelwright and machinist.

Elected as a Republican to represent the Seventeenth Congressional District of Ohio in the Thirty-Sixth Congress, he failed to win re-election in 1860, but was appointed to a seat on the U.S. Patent Office's Board of Appeals.

On August 15, 1865, he was appointed commissioner of the Patent Office, a post he held until his resignation in January 1868.