Henry Plummer (1832–1864) was a prospector, government bureaucrat, law enforcement officer and outlaw in the American west in the 1850s and 1860s. He was the elected sheriff of Bannack, Montana from 1863 to 1864, during which he was accused of being the leader of a "road agent" gang of outlaws known as the "Innocents". On from January 10, 1864 he was arrested in Bannack by a company of the Vigilance Committee of Alder Gulch and summarily hanged along with two other "road agents".