Blood and Black Lace (Italian: 6 donne per l'assassino, lit. '6 Women for the Murderer') is a 1964 giallo film directed by Mario Bava and starring Eva Bartok and Cameron Mitchell. The story concerns the brutal murders of a Roman fashion house's models, committed by a masked killer in a desperate attempt to obtain a scandal-revealing diary.

The film began development shortly after Bava had ended his long-time association with Galatea Film, for whom he had made most of his earlier works as a cinematographer and director. Made with a budget that was lower than several of the director's prior horror films, Blood and Black Lace was an Italian, French and West German international co-production between Emmepi Cinematografica, Les Productions Georges de Beauregard and Monachia Film. Different sources and ministerial papers provide varying degrees of information on the authorship of the film's screenplay, with most sources crediting Marcello Fondato, Giuseppe Barillà and Bava as co-writers; co-star Mary Arden is credited with having adapted the script's dialogue into English. Most of the technical staff and several cast members were veterans of Bava's previous films. Principal photography began in Rome in late 1963 with an international, multilingual cast; some actors read their lines fluently, while others performed them phonetically.

Film critics and historians such as Tim Lucas and Roberto Curti have identified Blood and Black Lace as representing an evolution in both Bava's style and the thriller genre depicted in cinema. Having used thriller conventions in his earlier films The Girl Who Knew Too Much and "The Telephone", a segment of Black Sabbath, Bava used this film to combine elements of contemporary West German murder mystery films (krimis) with the lurid juxtaposition of eroticism and violence present in popular fiction of the time, namely the long-running Giallo Mondadori series of pulp novels. Though it did not start a trend in the genre, the film has retrospectively been described as being among the first giallo films, as its exaggerated use of colour photography and eschewing of a traditional mystery in favour of a focus on set pieces of graphic murder would become staples of the form.

The film premiered in Rome on March 14, 1964, where it was commercially unsuccessful. Contemporary and retrospective reviews primarily praised Bava's direction and its visual style, although some found its plot to be weak and lacking in characterisation. After the successful release of Dario Argento's The Bird with the Crystal Plumage in 1970, a wave of gialli were made in Italy, with many sharing stylistic traits from Blood and Black Lace. Works by such filmmakers as Martin Scorsese and Pedro Almodóvar have referenced the film, and it has appeared on several "best of" lists related to thriller, horror and slasher films.