Robert LeRoy Parker (April 13, 1866 – November 7, 1908), better known as Butch Cassidy, was an American train and bank robber and the leader of a gang of criminal outlaws known as the "Wild Bunch" in the Old West.
Parker engaged in criminal activity for more than a decade at the end of the 19th century and the early 20th century, but the pressures of being pursued by law enforcement, notably the Pinkerton detective agency, forced him to flee the United States. He fled with his accomplice Harry Longabaugh, known as the "Sundance Kid", and Longabaugh's girlfriend Etta Place. The trio traveled first to Argentina and then to Bolivia, where Parker and Longabaugh are believed to have been killed in a shootout with the Bolivian Army in November 1908; the exact circumstances of their fate are unclear.