Burton Stephen "Burt" Lancaster (November 2, 1913 – October 20, 1994) was an American film actor and star, noted for his athletic physique, distinct smile (which he called "The Grin") and, later, his willingness to play roles that went against his initial "tough guy" image. Initially dismissed as "Mr Muscles and Teeth", in the late 1950s Lancaster abandoned his "all-American" image and gradually came to be regarded as one of the best actors of his generation.

Lancaster was nominated four times for Academy Awards and won once, for his work in Elmer Gantry in 1960. He also won a Golden Globe for that performance, and BAFTA Awards for The Birdman of Alcatraz (1962) and Atlantic City (1980).

Lancaster was born in New York City, the son of Elizabeth (née Roberts) and James Henry Lancaster, who was a postman. Both of his parents were Protestants of working-class Irish origin, with Lancaster's grandparents having been immigrants to the U.S. from Belfast and descendants of English immigrants to Northern Ireland. Lancaster's family believed themselves to be related to Frederick Roberts, 1st Earl Roberts; their surname originates from 11th century French immigrants to England with the surname "de Lancastre". Lancaster grew up in East Harlem and spent much of his time on the streets, where he developed great interest and skill in gymnastics while attending the DeWitt Clinton High School. Later, he worked as a circus acrobat until an injury forced him to give up the profession. During World War II, Lancaster joined the United States Army and performed with the USO.