Lou Costello, American actor and comedian (b. 1906)
Louis Francis Cristillo (March 6, 1906 – March 3, 1959), professionally known as Lou Costello, was an American comedian and actor. He was best known for his double act with straight man Bud Abbott and their routine "Who's on First?".

The comedians, who teamed up in burlesque in 1936, were among the most popular and highest-paid entertainers in the world during World War II. During a national tour in 1942 they sold $85 million in war bonds in 35 days. By 1955, their popularity waned due to overexposure, and their film and television contracts lapsed. Their partnership ended in 1957.