Sidney Edgerton (August 17, 1818 – July 19, 1900) was a politician, lawyer, judge and teacher from Ohio. He served during the American Civil War, as a Squirrel Hunter. During this time, Edgerton served as a U.S. Congressman. In 1863, Abraham Lincoln appointed him the first Chief justice of the Idaho Territorial Court. Edgerton lobbied for the creation of separate territories, out of the Idaho Territory, and in 1864, Abraham Lincoln appointed Edgerton as the first Territorial Governor of Montana. During his term as Territorial Governor, he was an alleged member of the infamous Montana Vigilantes, and was reputedly among its founders.