Underworld

Underworld can also refer to the movie series that includes Underworld, but also Underworld: Evolution and Underworld: Awakening.

Overview
Underworld is a 2003 American werewolf/vampire film. It is about a medical intern in Budapest, Hungary, named Michael Corvin who is sought out by both vampires and Lycans (werewolves) because of a gene he has. He is on the run from both of them, but when he is caught, the Lycan Lucian bites him, turning him into a werewolf.

Meanwhile, he has developed a romantic relationship with Selene, a vampire woman who is trained in assassinating werewolves.