Jack Harold Paar (May 1, 1918 – January 27, 2004) was an American radio and television talk show host most noted for his stint as host of The Tonight Show.

Paar was born in Canton, Ohio, the son of Howard and Lillian M. Paar. He moved with his family to Jackson, Michigan, 30 miles south of Lansing, as a child. Paar left school at 16. He first worked near home as a radio announcer at WIBM in Jackson and later as a humorous disc jockey at Midwest stations, including WJR in Detroit, WIRE in Indianapolis, WGAR in Cleveland and WBEN in Buffalo. In his book P.S. Jack Paar, he recalled doing utility duty at WGAR on the night Orson Welles broadcast his famous War of the Worlds over the CBS network (and affiliate WGAR). Attempting to calm possible panicked listeners, Paar announced, "The world is not coming to an end. Trust me. When have I ever lied to you?"

During World War II, as part of a special services company entertaining troops in the South Pacific, Paar was a clever, wisecracking master of ceremonies. More than once, his pointed jibes at officers nearly got him into trouble. After WWII, he came to the attention of RKO Radio Pictures, which hired him to emcee Variety Time (1948), a compilation of vaudeville sketches. Paar later recalled that RKO didn't know what to do with him. His producers, trying to decide what kind of screen characters he could play, compared Paar with other RKO stars. Finally, according to Paar, one of the executives had an inspiration, and figured out who Jack Paar really was: "Kay Kyser, with warmth." Paar projected a pleasant personality on film, and RKO called him back to emcee another filmed vaudeville show, Footlight Varieties (1951). Paar was featured in a few films, including a role opposite Marilyn Monroe in Love Nest (1951).