John Pierce St. John (February 25, 1833 - August 31, 1916) was an American politician during the 19th century. Born in Brookville, Indiana, he served as a colonel in the Union Army during the American Civil War.

St. John served in the Kansas State Senate in 1873 and was the Republican Governor of Kansas from 1879-1883. He was the Prohibition Party candidate for President of the United States in the 1884 election. He received 147,482 votes (about 1.5%) on a ticket with William Daniel.