Spencer Oliver Fisher (February 3, 1843 – June 1, 1919), was a politician from the U.S. state of Michigan.

Fisher was born in Camden, Michigan, where he attended the public schools.

He was an unsuccessful candidate for reelection in 1888, being defeated by Frank W. Wheeler, and resumed his former business pursuits in Bay City.

Fisher was a candidate for Governor of Michigan in 1894, but was defeated by the Republican incumbent John Tyler Rich.

He died twenty-five years later at the age of seventy-six in Bay City and is interred there in Elm Lawn Cemetery.