John Simpson Chisum (August 16, 1824 – December 22, 1884) was a wealthy cattle baron in the American West in the mid-to-late 19th century. He was born in Hardeman County, Tennessee, and moved with his family to the Republic of Texas in 1837, later finding work as a building contractor. He also served as county clerk in Lamar County. He was of Scottish, English, and Welsh descent.
In 1854, Chisum became engaged in the cattle business and became one of the first to send his herds to New Mexico Territory. He obtained land along the Pecos River by right of occupancy and eventually became the owner of a large ranch in the Bosque Grande, about forty miles south of Fort Sumner, with over 100,000 head of cattle. In 1866-67, Chisum formed a partnership with cattlemen Charles Goodnight and Oliver Loving to assemble and drive herds of cattle for sale to the United States Army in Fort Sumner and Santa Fe, New Mexico, to provide cattle to miners in Colorado as well as provide cattle to the Bell Ranch.
A gambler, Chisum frequently played poker with John Horton Slaughter, a lawman in Texas and later the Arizona Territory.
Chisum died in Eureka Springs, Arkansas, on December 23, 1884, aged 60, due to complications from surgery to remove a growth from his jaw. He was unmarried and left his estate worth $500,000 to his brothers Pitzer and James. Chisum had an extended family living with him at the South Springs ranch in Roswell, and this family, along with hired help, often numbered two dozen at the main ranch headquarters. Chisum's niece Sallie Lucy Chisum, daughter of his brother James, became a beloved figure in the area, where she lived until 1934. Sallie kept a diary or journal that has historical importance because of its references to Billy the Kid and Pat Garrett, both of whom she knew. She and John Chisum are honored by statues to their memory in Artesia and Roswell, New Mexico.
Chisum's story has been portrayed on film by John Wayne in Chisum (1970) and James Coburn in Young Guns II (1990).