Scott Speedman
Michael Sheen
Shane Brolly
Bill Nighy
Sophia Myles
Zita Görög

- The movie was initially pitched as "Romeo and Juliet for vampires and werewolves".
- The actors only had two weeks of wirework and prop training for the movie.
- At the start of the movie when Selene encounters a werewolf in the train tunnel, you hear a wolf howl - the sound effect is taken directly from An American Werewolf in London (1981).
- The ancient tome which Selene uses to research the history of Kraven is a Latin prayerbook (with appropriately vampiric illustrations added). The first two pages visible onscreen contain the "Proper of the Second Mass for All Souls Day" and the second set are Psalms. The rest of the pages are shown too far from the camera to make out clearly.
- The woman in the picture Selene finds in Michael's apartment is the wife of writer Danny McBride.
- 'Selene', the heroine's name, is the Moon in Greek mythology.
- After the underground station fight, the tunnels where Selene kills a Lycan are a champagne cellar.
- According to writer/actor Kevin Grevioux, the model for the Selene character was the psychic vampire of the Hellfire Club in the X-Men comics, the Black Queen Selene.
- A kiss between Michael and Selene (when she unchains him in Lucian's lab) appears in the trailer but was not included in the theatrical release or on the DVD, but it is on the unrated version of Underworld.
- Kate Beckinsale first met future husband Len Wiseman on the set.
- Scott Speedman suffered a concussion when a set prop that was supposed to be a piece of the wall Viktor had just thrown him through hit him in the head.

- Selene: I am a Death Dealer, sworn to destroy those known as the Lycans. Our war has waged for centuries, unseen by human eyes. But all that is about to change.
- Selene: It wasn't the Lycans. It was you. How could you bare my trust knowing that you killed my family?
- Selene: And the life of your daughter? Your own flesh and blood?
- Selene: Lycans are allergic to silver. We have to get the bullets out quickly, or they end up dying on us during questioning.
- Selene: We put the bullets back in.
- Selene: How can you trust him over me?
- Selene: Whether you like it or not, you're in the middle of a war that has been raging for the better part of a thousand years. A blood feud between vampires and lycans. Werewolves.
- Selene: Why are you helping me?
- Selene: But I've given you all the proof you need.
- Selene: But I did see Lucian, I shot him, you must believe me.
- Selene: But I had no choice, the coven is in danger and Michael is the key...
- Selene: [voiceover] The war had all but ground to a halt in the blink of an eye. Lucian, the most feared and ruthless leader ever to rule the Lycan clan, had finally been killed. The Lycan horde scattered to the wind in a single evening of flame and retribution. Victory, it seemed, was in our grasp, the very birthright of the vampires. Nearly six centuries had passed since that night, yet the ancient feud proved unwilling to follow Lucian to the grave. Though Lycans were fewer in number, the war itself had become more perilous, for the moon no longer held her sway. Older, more powerful Lycans, were now able to change at will. The weapons had evolved, but our orders remained the same: Hunt them down and kill them off, one by one. A most successful campaign. Perhaps too successful. For those like me, a Death Dealer, this signaled the end of an era. Like the weapons of the previous century, we, too, would become obsolete. Pity, because I lived for it.
- Selene: [voiceover] Though I cannot predict the future, the consequences of this night will reverberate through the halls of both great covens for many years to come. Two vampire elders have been slain, one by my own hand. Soon, Marcus will take the throne, and a tide of anger and retribution will spill out into the night. Differences will be set aside. Allegiances will be made. And soon, I will become the hunted.
- Selene: Not before you.
- Selene: I've been lost without you, my Lord; constantly hounded by Kraven and his never-ending infatuation.
- Selene: I know.
- Selene: Kraven, I'm serious!
- Selene: Jump.
- Selene: We have a serious problem.

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