This trope is Exactly What It Says on the Tin. When Romance Ensues in a continuity featuring Fur Against Fang, the result tends to end up including a Love Triangle featuring a vampire and a werewolf as two of the three members. Generally the central figure is a human, but not always.
Usually also involves Feuding Families, Fur Against Fang, Maligned Mixed Marriage, Star-Crossed Lovers, Romantic Vampire Boy. Compare Muggle-and-Magical Love Triangle, this trope's main competitor in the Paranormal Romance genre. May overlap with Monster/Slayer Romance if the human ordinarily hunts vampires or werewolves.
- In Dance in the Vampire Bund, Mina's the vampire, Akira is the werewolf, and the Royal Three make up the third party as a whole. There's also the odd triangle between Mina, Akira, and Yuki, who is in love with Akira and has a lot of mutual Les Yay with Mina.
- In Inuyasha, Tsundere Kagome likes InuYasha (who is a dog hanyou, which is similar to a werewolf), and he used to love Kikyo (Kagome's past life), who becomes essentially an undead soul — energy eater, and Koga, a wolf youkai, is in love with Kagome.
- Princess Resurrection contains a distaff counterpart where a female werewolf Liza and a female vampire Reiri are both attracted to Unlucky Everydude human male. In actuality, neither sees him as a romantic interest, more as a plaything or underage drinking buddy. Now, how they, especially Reiri, view his mistress Hime on the other hand...
- In Millennium Snow, Toya is the vampire and Satsuki is the werewolf. The girl they are competing for is Chiyuki.
- Played totally straight in the Twilight series with Bella (human), Edward (vampire) and Jacob (werewolf).
- Amusingly subverted in Underworld. Vampire Kraven thinks he's in a love triangle with Vampire Assassin Selene and the series' Unfazed Everyman, Michael. And the werewolves are trying to turn Michael to their side before she gets a hold of him. He's dead wrong, though, since she thinks he's a power-hungry coward. Hell, at that point in the story, she doesn't even have a romantic interest in Michael yet... Kraven is just so narcissistic as to think she's in love with him, and it infuriates him to even consider that she could choose Michael over him.
Of course, she does eventually fall in love with Michael, despite him being turned into a werewolf against his will. She even tries mightily to protect him from other vampires and herself (considering she usually kills werewolves on sight). Kraven tries to win her over again (despite having been exposed as a traitor to all vampires) and at this time she literally shoots him down, though she fails to kill him (not for lack of trying). He dies in the second movie.
- Played With in Van Helsing: the title character is in the process of becoming a werewolf when Dracula kidnaps his love interest and tries to seduce her. Said Love Interest is also the main character of Underworld described above.
- Anita Blake. In addition to being a love triangle, the metaphysical bonds formed between the human necromancer, the vampire, and the werewolf makes all of them more powerful.
- In the Discworld book Thud, Angua the werewolf is in a relationship with Carrot, but Sally the vampire develops a crush on him and an intense rivalry develops between the girls, which is only intensified by instinctual Fur Against Fang. However, the rivalry (and instinctual dislike) seems to be mostly in Angua's mind. Sally admits that she's attracted to Carrot, but knows that she doesn't really have a chance; his heart beat picks up whenever Angua is around.
- Somewhat true in Patricia Briggs' Mercy Thompson books. The titular character has to choose between two werewolves: teenage crush Samuel and next-door-neighbor Adam, but she also has a rather close relationship with vampire Stefan, whose unrequited crush seems very likely to stay unrequited. In the fifth book she finally chooses Adam, but this remains pretty central to the plot for most of the series. However, Stefan is only really a contender in his own mind, as Mercedes has plenty of good reasons to dislike vampires.
- Played With in The Mortal Instruments, when a love triangle develops with vampire Simon in the middle of werewolf Maya and human/Shadowhunter Isabelle.
- Another example of this trope is Daniel Gonzalez's Ravencraft novels, theres a love triangle between vampire hunter Donovan Fort, his vampire girlfriend Lucilla and his werewolf colleague Laura Talbot.
- The Sookie Stackhouse Mysteries and its HBO adaptation, True Blood. Okay, he's an Animorphism shapeshifter. But he gets mistaken for a werewolf. If you read further into The Sookie Stackhouse Mysteries, it's actually a telepath / vampire / vampire / shapeshifter / werewolf / werepanther / weretiger Love Dodecahedron. On the other hand, Sookie breaks up with/kills most of her past lovers before moving onto the next one, so it's not quite such a tangled mess. Not to mention, with Harris' habit of killing off characters left and right, there likely soon won't be any characters left for Sookie to even have a relationship with, let alone have to worry about sparking rivalries.
- Twilight: The Trope Codifier, as this is, fundamentally, the whole plot of the series. The first book establishes the romance between human Bella and Romantic Vampire Boy Edward. The second has Bella get closer with her childhood friend, Jacob, while revealing that he's the Magical Native American version of a werewolf. The triangle continues through two more books, weirdly ending with Edward and Bella getting married, conceiving a fast-growing Dhampyr on their honeymoon, and giving her and Jacob a Hooked Up Afterwards. Some evil vampires are thrown in to pad the story.
- Hemlock Grove: Zigzagged. Vampire Roman Godfrey and werewolf Peter Rumancek were already best friends before they met the human Miranda. When she convinces them to have a threeway with her, they both feel weird about it the next morning, but they're never shown fighting over her.
- House of Frankenstein (1997) features vampire (the Big Bad), the Love Interest (a woman bitten by a werewolf) and the hero (the cop). Lampshaded when a monster expert mentions that vampires love lycanthropes; "Their own little animal — you know what men are like."
- Season three of Penny Dreadful features a major love triangle between werewolf Ethan Chandler, Apocalypse Maiden Vanessa Ives, and Dracula.
- The Vampire Diaries starts playing with it in the second season, with Caroline developing an intense friendship and bond with Tyler while still having some feelings for her ex-boyfriend Matt. Season 3 takes it further as Tyler has also become a vampire, and Klaus, who is also vampire and werewolf. In short, it's a vampire girl torn between two werewolf-vampire hybrids.
- The Originals twists this somewhat with the Elijah/Hayley/Jackson triangle. Jackson loves Hayley but they end up marrying for power and after Jackson dies she rekindles her romance with Elijah.
- Wizards of Waverly Place twists this around with Juliet briefly falling into one between Justin and Mason.
- Young Dracula is an example of this, because Vlad's mother ran off with a werewolf. In this case, that means a vampire running away from her vampire husband (and children) to a werewolf lover.
- Averted in the Girls' Love Visual Novel Akai Ito, despite having premise of Lesbian Vampire versus Beastess and each of them have a route. Due to the way the routes are written, you can't connect to another character when you're already connected to someone.
- A weird version of this appears to be going on between Vulcanus/Valvatorez/Fenrich in Disgaea 4. Of note to what makes it weird: There's no human in the triangle (Vulcanus is an angel though she was formerly a human), the vampire is at the center of the triangle, and both the vampire and the werewolf are male. There is, however, a Bad End where Token Human Fuka makes Valvatorez and Fenrich her harem. They're not happy with it, particularly since she makes them wear maid outfits.
- Batman: The Animated Series features a rather unorthodox example in the episode Tyger, Tyger. Selina Kyle is being fought over by Batman, who's a man only dressed as a bat, and a Werecat.
- In a Halloween Episode of The Cleveland Show, Roberta believes she's being fought over between a mysterious vampire and loner werewolf. Subverted, when it's revealed that both the monsters are actually gay for each other.
- In the Fillmore! episode, "The Unseen Reflection", features this as part of a Show Within a Show.
- In the Monster High Valentines Day special, Clawd the werewolf is trying to figure out what to get Draculaura for her birthday. Enter her ex-boyfriend, the charming vampire Valentine...