Prosper Powell Parker (December 26, 1835 – March 16, 1918) was a Canadian-born American engineer and politician. During the American Civil War he served as a junior officer under General William T. Sherman, rising to the rank of captain. Following the war he served on the committee that organized Towner County, North Dakota before moving to Arizona Territory. In Arizona he was twice elected to the territorial legislature and became Speaker of the House during the 21st Arizona Territorial Legislature.