Born in Emporia, Kansas, Ermey enlisted in the United States Marine Corps in 1961. He spent two years as a drill instructor at the Marine Corps Recruit Depot in San Diego, California. Ermey then served two tours of duty in Vietnam and Japan, where he rose to the rank of Staff Sergeant. He was honorably discharged in 1972.
Ermey was cast in his first movie while he studied at the University of Manila in the Philippines. He played a helicopter pilot in Apocalypse Now, and also served as a technical advisor to director Francis Ford Coppola. He played minor roles in films until 1987, when he was cast as the sadistic drill instructor in Stanley Kubrick's Full Metal Jacket.
He has since appeared in numerous films, including Mississippi Burning, Se7en, Prefontaine, Saving Silverman, and the remakes of Willard and The Texas Chainsaw Massacre. Ermey also lent his voice for Toy Story, Toy Story 2, and an episode of The Simpsons.
Ermey is now the host of Mail Call, a military history program on the History Channel.