Butch Cassidy (13 April 1866 - c. 1908?) was a notorious train and bank robber.

Robert LeRoy Parker was born in Beaver, Utah, to Maximillian Parker and Ann Campbell Gillies, English Mormon and Scottish immigrants to the Utah Territory. His parents were residents of Victoria Road, Preston, Lancashire but fled England due to religious persecution for their Mormon faith. He grew up on his parents' ranch near Circleville, Utah, some 215 miles south of Salt Lake City, Utah.

Parker left home during his early teens and, while working at a dairy farm, he fell in with Mike Cassidy, a horse thief and cattle rustler. He subsequently worked several ranches in addition to a brief stint as a butcher in Rock Springs, Wyoming, when he acquired the nickname "Butch", to which he soon appended the surname Cassidy in honor of his old friend and mentor. (A "Butch" is also the name given to a borrowed gun.)

Parker's first brush with the law was a petty affair. At the age of about 14 (c 1880) he made a long journey to a clothier's shop in another town only to find the place shut. So, letting himself in, he removed a pair of jeans and left an IOU to the effect that he would pay for it upon his next visit. However the clothier took down the details which Parker had included in the IOU and reported him. After a stubborn resistance to the resultant charges in court, he was acquitted despite his having broken into the premises.