Sam Spade is a fictional character and the protagonist of Dashiell Hammett's 1930 novel The Maltese Falcon. Spade also appeared in four lesser-known short stories by Hammett.

The Maltese Falcon, first published as a serial in the pulp magazine Black Mask, is the only full-length novel by Hammett in which Spade appears. The character, however, is widely cited as a crystallizing figure in the development of hard-boiled private detective fiction—Raymond Chandler's Philip Marlowe, for instance, was strongly influenced by Spade.

Spade was a departure from Hammett's nameless and less-than-glamorous detective, the Continental Op. Spade combined several features of previous detectives, most notably his detached demeanor, keen eye for detail, and unflinching determination to achieve his own justice.

Spade was a new character created specifically by Hammett for The Maltese Falcon; he had not appeared in any of Hammett's previous stories. Hammett says about him:

Spade has no original. He is a dream man in the sense that he is what most of the private detectives I worked with would like to have been and in their cockier moments thought they approached. For your private detective does not—or did not ten years ago when he was my colleague—want to be an erudite solver of riddles in the Sherlock Holmes manner; he wants to be a hard and shifty fellow, able to take care of himself in any situation, able to get the best of anybody he comes in contact with, whether criminal, innocent by-stander or client.

From the 1940s onward, the character became closely associated with actor Humphrey Bogart, who played Spade in the third and best-known film version of The Maltese Falcon. Though Bogart's slight frame, dark features and no-nonsense depiction contrasted with Hammett's vision of Spade (blond, well-built and mischievous), his sardonic portrayal was well-received, and is generally regarded as an influence on both film noir and the genre's archetypal private detective.

Spade was played by Ricardo Cortez in the first film version, released in 1931. Despite being a critical and commercial success, an attempt to re-release the film in 1936 was denied approval by the Production Code Office due to the film's lewd content. Since Warner Bros. could not re-release the film, a second version, this one a comedy, Satan Met a Lady (1936), was produced. The central character was renamed Ted Shane and was played by Warren William. The film was a box-office failure, and eventually resulted in a new version being made starring Bogart and directed by John Huston, which closely followed the novel, with a few exceptions.

George Segal played Sam Spade, Jr., son of the original, in the film spoof The Black Bird (1975). The Black Bird was panned by critics. Peter Falk delivered a more successful spoof the following year as Sam Diamond in Neil Simon's Murder by Death. This was preceded by the spoof character Sam Diamond in The Addams Family episode "Thing Is Missing" (1965) portrayed by Tommy Farrell.