The St. Valentine's Day Massacre is a 1967 American gangster film based on the 1929 mass murder of seven members of the Northside Gang (led by George "Bugs" Moran) on orders from Al Capone. The picture was directed by Roger Corman, written by Howard Browne, and starring Jason Robards Jr. as Capone, Ralph Meeker as Moran, George Segal as Peter Gusenberg, and David Canary as Frank Gusenberg.

Corman, better known as a director and producer of low-budget B movies, was given his largest budget to date (estimated at $2.5 million) and the backing of 20th Century Fox to realize what he described as "the most accurate, authentic gangster film ever". With a voiceover narration by Paul Frees, the film depicts in detail the events leading up to the massacre in a docudrama-style, with many authentic historical details.

A young Bruce Dern plays one of the victims of the massacre, and Jack Nicholson has a bit part as a gangster. Also featured are Jan Merlin as one of Moran's lieutenants and veteran Corman actor Dick Miller as one of the phony policemen involved in the massacre. Leo Gordon makes an early screen appearance as Heitler.