Born January 3, 1929, in Rome, Leone was the son of the cinema pioneer Vincenzo Leone (known as director Roberto Roberti or Leone Roberto Roberti) and silent film actress Edvige Valcarenghi (Bice Valerian). During his schooldays, Leone was a classmate of his later musical collaborator Ennio Morricone for a time. After watching his father work on film sets, Leone began his own career in the film industry at the age of 18 after dropping out of law studies at the university.