The Honeymoon Killers is a 1970 American crime film written and directed by Leonard Kastle, and starring Shirley Stoler and Tony Lo Bianco. Its plot follows an overweight nurse who is seduced by a handsome con man, with whom she embarks on a murder spree of single women. The film was inspired by the true story of Raymond Fernandez and Martha Beck, the notorious "lonely hearts killers" of the 1940s.

Filmed primarily in Pittsfield, Massachusetts, production of The Honeymoon Killers began with Martin Scorsese as its appointed director. However, after Scorsese was fired early into the shoot, he was replaced by Donald Volkman, a maker of industrial films, who lasted only two weeks before Kastle, who had helped develop the film, took over directing. The film's score comprises the first movement of the 6th Symphony and a section of the 5th Symphony of Gustav Mahler. Released in early 1970, the film was met with critical praise for its performances as well as its realism.

The Honeymoon Killers went on to achieve cult status as well as critical recognition, and was named by François Truffaut as his "favorite American film." A digital restoration of the film was released on DVD by The Criterion Collection in 2003, and again in 2015 with a new digital transfer.