The Girl Who Knew Too Much (Italian: La ragazza che sapeva troppo) is a 1963 Italian giallo film directed by Mario Bava, starring John Saxon as Dr. Marcello Bassi and Letícia Román as Nora Davis. The plot revolves around a young American woman named Nora, who travels to Rome and witnesses a murder. The police and Dr. Bassi do not believe her, since a corpse has not been found. Several more killings follow, tied to a decade-long string of murder victims chosen in alphabetical order.

The Girl Who Knew Too Much is considered to be the first giallo film, a film genre with a mixture of thriller, sexploitation and horror conventions. An alternative cut titled The Evil Eye was released in the United States and the United Kingdom by American International Pictures; this version features a score by Les Baxter, deletes several scenes, and adds others which place a greater emphasis on comedy compared to the Italian release.