John Calhoun Cook (December 26, 1846 – June 7, 1920) was a 19th-century American politician, lawyer and judge from Iowa. He was twice elected to the U.S. House of Representatives from Iowa's 6th congressional district, each time under unusual circumstances. Born in Seneca, Ohio, just two days before Iowa was admitted as a state, Cook attended common schools as a child, studied law and was admitted to the bar in 1867, commencing practice in Newton, Iowa. He was judge of the sixth judicial district of Iowa in 1878.