John Fetzer (July 8, 1840 – after 1895) was an American politician. He was a member of the Wisconsin State Senate, representing Wisconsin's 1st Senate District. Previously, he held a position in the State Assembly. He was a member of the Democratic Party.
Fetzer was born in Pigelheim, Hesse-Darmstadt, Germany. He moved to Manitowoc, Wisconsin in 1850, and then to Forestville in 1867 after serving in the Civil War.
In September 1861, he enlisted in Company B, of the 9th Wisconsin Volunteer Infantry Regiment. He served until December 1864. He was engaged in all of the battles in which his regiment participated, and was wounded at the Battle of Saline Bottoms on April 30, 1864.
He was the chairman of the Forrestville town board for many years, before becoming a member of the State Assembly, and later the State Senate.