Murder in a Blue World (Spanish: Una gota de sangre para morir amando, lit. A Drop of Blood to Die Loving; French: Le bal du vaudou, lit. The Voodoo Ball) is a 1973 Spanish-French dystopian science fiction/crime/horror film directed by Eloy de la Iglesia and starring Sue Lyon, Christopher Mitchum and Jean Sorel.

The plot follows a respectable nurse, who seduces young men, takes them home to bed, listens to the post-coital beating of their hearts, and then stabs them to death with a surgical scalpel. The film takes some cues from Stanley Kubrick's A Clockwork Orange to the extent of being released on UK VHS as Clockwork Terror.