August Theodor Koerner (July 7, 1843 – April 17, 1912) was an American businessman and politician.

[1] He emigrated to the United States in 1857 and settled in Vernon, Indiana, working in a mill.

During the American Civil War, Koerner served in the 6th Indiana Infantry Regiment.

He served as Litchfield Village Clerk and as Meeker County Register of Deeds.

[1] He died in the Mounds Park sanatorium in St. Paul from heart problems on April 17, 1912.