Goodnight Sweetheart is a British science fiction time travel sitcom, starring Nicholas Lyndhurst, created by Laurence Marks and Maurice Gran, and produced by the BBC. The sitcom is about the life of Gary Sparrow, an accidental time traveller who leads a double life through the use of a time portal, which allows him to travel between the London of the 1990s and the London of the 1940s during the Second World War. The sitcom's creators, who also created Birds of a Feather and The New Statesman, wrote most of the plots for the episodes.

The sitcom premiered on BBC1 on 18 November 1993 and ran for six series until its conclusion on 28 June 1999, with repeats after this date being aired on ITV3, Gold, Drama, Yesterday and Forces TV on Sky Digital. Lyndhurst's involvement in the sitcom allowed him to win the Most Popular Comedy Performer at the National Television Awards in 1998 and 1999. On 2 September 2016, the sitcom received a one-off special entitled Many Happy Returns, following events after the final episode. The sitcom itself later received a musical adaptation in 2017.