Louis Francis Cristillo aka Lou Costello (March 6, 1906 - March 3, 1959) was an American actor, producer and comedian from Paterson, New Jersey. He is best known as half of the comedy team of Abbott and Costello, with Bud Abbott.

Costello worked as a carpenter at MGM and Warner Brothers after high school. After that, he worked temporarily as a stuntman, and then eventually became a vaudeville comedian.

In 1931, while performing in Brooklyn, New York, Costello's straight man became ill and the theater cashier, Bud Abbott, filled in.

Throughout the 1930s, Abbott and Costello performed together in burlesque shows, minstrel shows, vaudeville and movie houses.

At Costello's request, all profits earned from the act were split 60/40, favoring Abbott, because, according to Costello, "Comics are a dime a dozen. Good straight men are hard to find."

In 1938 they received national exposure for the first time by performing on the Kate Smith Hour radio show, which led to the duo signing with Universal the following year. Abbott and Costello appeared in their first film in 1940, a movie entitled One Night in the Tropics. Although Abbott and Costello were only filling supporting roles, they stole the film with their classic routine Who's On First?. (Abbott and Costello are the only two non-baseball players honored in the Baseball Hall of Fame museum in Cooperstown, New York, because of their legendary Who's On First? routine.) The team's breakthrough picture, however, was Buck Privates which was released in 1941. They immediately became the top ranking comedy stars in Hollywood and fans looked upon each of their pictures as a major event. Many of their films showed them as bumbling servicemen such as In The Navy and Abbott and Costello Join The Air Force. An amusing footnote to this is the Japanese military high command obtained copies of the teams films and showed them to Japanese soldiers in all seriousness! They told them that was how American military people really acted. In 1943, Costello suffered a severe heart attack and was unable to work for a year and a half. A tragic event shadowed his comeback. On the day Costello returned to do the team's popular radio show, his infant son drowned in an accident. He did the show as a tribute to his memory. People who knew Lou Costello said that he never recovered from the loss of his child.

Abbott and Costello split up in 1957, after troubles with the Internal Revenue Service that left both men broke.

After making one unsuccessful film as a solo act (The 30 Foot Bride of Candy Rock ) Costello died in 1959 from a heart attack and was interred in the Calvary Cemetery in East Los Angeles, California.