Giallo (Italian pronunciation: [ˈdʒallo], plural gialli) is a 20th-century Italian thriller or horror genre of literature and film. Especially outside of Italy, giallo refers specifically to a particular Italian thriller-horror genre that has mystery elements and often contains slasher, crime fiction, psychological thriller, psychological horror, and, less frequently, supernatural horror elements. In Italy, the term generally denotes thrillers, typically of the crime fiction, mystery, and horror subgenres, regardless of the country of origin.
In English-speaking countries, the term giallo often refers to the Italian film version of the genre, a particular style of Italian-produced murder mystery thriller-horror film that usually blends the atmosphere and suspense of thriller fiction with elements of horror fiction (such as slasher violence) and eroticism (similar to the French fantastique genre), and often involves a mysterious killer whose identity is not revealed until the final act of the film. The genre developed in the mid-to-late 1960s, peaked in popularity during the 1970s, and subsequently declined over the next few decades. (Some examples continue to be produced). It has been considered to be a predecessor to, and significant influence on, the later American slasher film genre.
The word "" is Italian for "yellow". The term was derived from a series of cheap paperback mystery novels, popular in post-fascist Italy, which were published with yellow covers.