Theodore Dieckmann (November 6, 1853 – October 6, 1919) was an American politician and businessman. Born in New York City, Dieckmann moved with his parents to Sheboygan, Wisconsin in 1858. Dieckmann owned a jewelry business in Sheboygan, Wisconsin. He served on the Sheboygan Common Council and was mayor of the city. In 1893, Dieckmann served in the Wisconsin State Assembly and was a Republican. Dieckmann died at his home in Sheboygan, Wisconsin.