Clifford Parker Robertson III was an American actor whose career in film and television spanned over six decades. Robertson portrayed a young John F. Kennedy in the 1963 film PT 109, and won the 1968 Academy Award for Best Actor for his role in the film Charly.

PT 109 is a 1963 American Technicolor Panavision biographical war film depicting the actions of John F. Kennedy as an officer of the United States Navy in command of Motor Torpedo Boat PT-109 in the Pacific theater of World War II. The film was adapted by Vincent Flaherty and Howard Sheehan from the book PT 109: John F. Kennedy in World War II by Robert J. Donovan, and the screenplay was written by Richard L. Breen. Cliff Robertson stars as Kennedy, and the film features performances by Ty Hardin, James Gregory, Robert Culp and Grant Williams.