Thomas Henry Armstrong (February 6, 1829 – December 29, 1891) was a Minnesota banker, lawyer, legislator, and the fifth Lieutenant Governor of Minnesota.

His father was born in Rhode Island but later moved to Milan, Ohio, where he married Phebe Higby.

Thomas studied in Milan, Ohio for a couple of years before moving to Minnesota in 1855, where he settled in High Forest, Minnesota.

Before the outbreak of the Civil war, he was originally a Douglas Democrat, but when the war broke out, he became a staunch Republican He stayed in High Forest until he moved to Albert Lea in April 1875.

In the autumn of 1874, he ran as an independent for the State Senate, an endeavor in which he was successful.