The Tonight Show is an American late-night talk show that has been broadcast on NBC since 1954. The program has been hosted by six comedians: Steve Allen (1954–1957), Jack Paar (1957–1962), Johnny Carson (1962–1992), Jay Leno, Conan O'Brien (2009–2010), and Jimmy Fallon (2014–present). Besides the main hosts, a number of regular "guest hosts" have been used, notably Ernie Kovacs, who hosted two nights per week during 1956–1957, and a number of guests used by Carson, who curtailed his own hosting duties back to three nights per week by the 1980s. Among Carson's regular guest hosts were Joey Bishop, McLean Stevenson, David Letterman, David Brenner, Joan Rivers, and Jay Leno, although the practice has been mostly abandoned since hosts currently prefer reruns to showcasing potential rivals. Fallon has used guest hosts rarely, co-hosting the May 24, 2021, broadcast with Dave Grohl, Jimmy Kimmel hosting the April 1, 2022, broadcast, Shawn Mendes co-hosting the April 29, 2022, broadcast, Megan Thee Stallion co-hosting the August 11, 2022, broadcast, Demi Lovato co-hosting the August 17, 2022, broadcast, and Jack Harlow co-hosting the October 6, 2022, broadcast.

A late-night talk show is a genre of talk show, originating in the United States. It is generally structured around humorous monologues about the day's news, guest interviews, comedy sketches and music performances. It is characterized by spontaneous conversation, and for an effect of immediacy and intimacy as if the host were speaking directly to each member of the watching audience. Late-night talk shows are also fundamentally shaped by the personality of the host.