Thomas P. Hannegan was an American businessman and politician from the state of Missouri. A Republican, Hannegan was elected to the Missouri House of Representatives from Missouri's 65th District in November 2016, and re-elected in 2018. He represented a portion of Saint Charles County north and northeast of the city of St. Charles to the Mississippi River. Hannegan also worked for a family-owned real estate business and as a magazine publisher and chief editor.