Thomas Lyon Hamer (July 1800 – December 2, 1846) was a Democratic congressman and soldier in the United States.

As Speaker, he sought to maintain independence from party politics; although Jackson's supporters controlled a slight advantage over John Quincy Adams' supporters, he appointed Adams men as a majority in seven of the fifteen standing committees.

Popular and well respected, Hamer was appointed a brigadier general of volunteers on July 1, 1846.

He was placed in command of the 1st Brigade of William O. Butler's Volunteer Division of the Army of Occupation.

When General Butler fell wounded, Hamer assumed command of the division.