"Underworld" is a dark fantasy action-horror film released in 2003. The film was directed by Len Wiseman and stars Kate Beckinsale, Scott Speedman, Michael Sheen, and Bill Nighy. It tells the story of a centuries-long war between vampires and werewolves, or lycans, and the humans caught in the middle.

In the film, Selene (Kate Beckinsale) is a vampire warrior who is dedicated to fighting against the lycans, whom she believes are responsible for killing her family. When she uncovers a plot by the lycans to create a hybrid creature that would give them the upper hand in the war, she finds herself in conflict with her own kind and teams up with a human, Michael Corvin (Scott Speedman), to stop the lycans' plan.

The film received mixed reviews upon its release but was a box office success, grossing over $95 million worldwide. It was praised for its stylized action sequences, gothic atmosphere, and strong performances, particularly by Kate Beckinsale as Selene. The success of the film spawned a franchise that includes four sequels and a spin-off.

The "Underworld" series is known for its depiction of a complex supernatural mythology, intense action sequences, and stylish gothic visuals. The franchise has a dedicated fan base and is considered a cult classic among horror and fantasy fans.