When Dinosaurs Ruled the Earth (titled When Dinosaurs Ruled the World in the U.K.) is a 1970 British fantasy film from Hammer Films, written and directed by Val Guest, and starring Victoria Vetri. It was produced by Aida Young. This was the third in Hammer's "Cave Girl" series, preceded by One Million Years B.C. (1966) and Prehistoric Women (1967); it was followed by Creatures the World Forgot (1971).