Marcus Reno was born in Carrollton, Illinois. He graduated from the U.S. Military Academy in 1857 and served in the cavalry during the Civil War.

He was an American officer who became known for his role in the Battle of the Little Bighorn where a bitter controversy began after the battle, and Major Reno was accused of cowardice.

Reno was cleared of the charges in 1879. He is buried at the Little Bighorn National Monument.