Thomas Harold Massie (born January 13, 1971) is an American politician and engineer. A member of the Republican Party, Massie has been the United States representative for Kentucky's 4th congressional district since 2012. The district covers much of northeastern Kentucky, but is dominated by the Kentucky side of the Cincinnati area and Louisville's eastern suburbs.

Before joining Congress, Massie was judge-executive of Lewis County, Kentucky, from 2011 to 2012. He also founded a startup company based in Massachusetts, where he previously studied at the Massachusetts Institute of Technology.

Massie is known for his advocacy of limited government, fiscal responsibility, and individual liberties, often aligning with libertarian principles in his voting record. Massie has been described as a libertarian Republican and a member of the Tea Party movement, which backed his candidacy for Congress in 2012. Massie has described himself as a "constitutional conservative," stating that his political philosophy is rooted in the belief that "the federal government should be strictly limited by the Constitution."