Underworld: Evolution is a 2006 American action horror film directed by Len Wiseman from a screenplay by Danny McBride, based on a story by Wiseman and McBride. It is the sequel to Underworld (2003) and the second installment in the Underworld film series. The film stars Kate Beckinsale, Scott Speedman, Tony Curran, Shane Brolly, Steven Mackintosh, Derek Jacobi, and Bill Nighy. The plot follows Selene and Michael, again played by Beckinsale and Speedman, respectively, as they fight to protect the Corvinus bloodline from its hidden past.

Underworld: Evolution premiered at the Cinerama Dome in Los Angeles, California on January 11, 2006, and was released in the United States on January 20, by Sony Pictures Releasing. The film received generally negative reviews from critics and grossed over $113 million worldwide against a production budget of $45 million.

The film was followed by the prequel Underworld: Rise of the Lycans in 2009 and later a direct sequel Underworld: Awakening in 2012.

In 1202, an army led by the three vampire elders (Markus, Viktor, and Amelia) arrives at a village full of Werewolves. Viktor and Amelia capture their target, Markus's twin brother, William Corvinus, the first and most powerful werewolf. Despite Markus's defiance, Viktor orders that William be forever imprisoned in a secret location.

In the present day, vampire Selene takes Michael to a safe house so that she can confront the vampire regent Kraven; she plans to stop Kraven from killing Markus. Markus awakens before Kraven arrives and kills him and his men. Lorenz Macaro, an elderly man, sends in a team to investigate the aftermath of the battle in the Lycans' lair. When Macaro examines Viktor's corpse he finds a metal disc which matches a pendant originally worn by Sonja. The other half of the pendant is possessed by Michael after Lucian's death.

Using the knowledge of computers obtained from Kraven's blood, Markus tracks Selene and Michael down and attacks them, but they evade him and hide in a warehouse. There, Selene and Michael share their feelings and have sex. Knowing that the pendant is important to Markus, Michael and Selene set out to discover why he wants it. Selene recalls that she saw it as a child, but does not know its significance. They travel to the hideout of the exiled vampire historian Andreas Tanis.

Tanis reveals that Markus was the first vampire, one of the three sons of Alexander Corvinus, the first immortal. Markus was bitten by a bat and metamorphosed into a vampire, while William was bitten by a wolf and metamorphosed into a werewolf. The third son remained human and gave rise to a line of mortal descendants including Michael, who became the first Lycan-Vampire hybrid. The first werewolves created by William were entirely feral and unable to return to their human forms. Due to William's destructiveness, Markus approached Viktor, then a dying mortal warlord, and offered to metamorphose him and his army into vampires in exchange for tracking down and stopping William, and destroying those he had infected. Viktor did not kill the brothers because he was led to believe that doing so would result in the immediate extinction of all vampires and Lycans. Tanis further reveals that Selene's father was the architect who built William's prison and that the pendant is the key. Viktor killed Selene's family because they knew the prison's location, but metamorphosed Selene into a vampire with the location of the prison encoded in her blood. Tanis then refers Selene and Michael to Macaro for help. After Selene and Michael leave, Markus arrives and drinks Tanis' blood to learn Selene and Michael's location, killing Tanis.

Visiting Macaro, Selene and Michael discover he is Alexander Corvinus, the forefather to both the vampire and Lycan races. Alexander reveals that he has devoted his entire immortal life to keeping the Vampire-Lycan war a secret, and refuses to assist Selene in killing his sons. Markus arrives, fights Michael and impales him. He learns the location of William's prison by drinking Selene's blood before mortally wounding his father and obtaining the other half of the pendant. He mocks his father's refusal to help William, revealing that he intends, with William, to rule the world as the master of a race of vampire-Lycan hybrids. At Alexander's bidding, Selene drinks his blood, enhancing her physical strength and healing abilities to a level equivalent to that of a hybrid. Afterwards, Alexander blows up his ship, killing himself.