Serial Romeo

"Did my heart love till now? Foreswear it, sight;

For I ne'er saw true beauty till this night!"

- Romeo, from Romeo and Juliet

"Bingo: Her name is Mertle. Isn't she beautiful!

Bertie: What happened to Daphne?

Bingo: Daphne?

Bertie: The one who came after Honoria?

Bingo: Bertie, fancy, Bertie, the folly of one's youth!

Bertie: It was only a week and a half ago."

- Jeeves and Wooster

This character is a hopeless romantic. He's madly, passionately, fatally devoted to the girl he loves. It's just that the girl he loves seems to change from week to week. When one girl rejects him (which she usually does), he is heartbroken at first, but he soon finds a new love interest, and forgets all about the old one.

Unlike the Casanova, who strings many women along at the same time without caring about any of them, the Serial Romeo genuinely believes that each successive love is "The One", and that without her, life is not worth living. Expect this character to be completely blind to the implications of having a new "True Love" every week. If called out on his fickleness, expect him to insist that his current love interest is the only person he has ever really loved, and to dismiss her predecessors as mere youthful infatuations. Expect much eye-rolling from his friends.

Note: Although this trope usually applies to heterosexual men, feel free to put female or homosexual examples here.

See also Looking for Love In All the Wrong Places, Girl of the Week, and In Love with Love.

Anime and Manga

 * The Pokémon anime has Brock. But it's not (usually) because he gets rejected, but he keeps being stopped and pulled away by Misty (pulling by the ear), Max (after getting it from the former), May (on one occasion), his Bonsly (only a few times with Double-Edge), or his Croagunk (with a Poison Jab, no less).
 * In recent episodes, Ash's Oshawott seems to be becoming this.
 * Martina of Slayers Next falls madly in love with just about every male member of the cast she meets. The fixation on Zangulus at the end of the season lasts long enough to get her married off.
 * Claire Stanfield from Baccano has a habit of falling in Love At First Sight with basically every girl ever, proposing to them in all seriousness at their first meeting.

Film

 * Sameer from the Bollywood movie Dil Chahta Hai. Unlike his friend Akash, who is a Casanova, Sameer believes that he is truly in love which each new pretty girl he meets, and is heartbroken when they reject him. His despairing parents eventually try to set him up in an arranged marriage with a girl named Pooja. Fortunately, Sameer ends up falling in love with her, too!

Literature

 * Very much the case with Neal from Tamora Pierce's Protector of the Small quartet, although he eventually gets over it and gets married.
 * The Encyclopedia Brown series has Kidanova Tyrone Taylor.
 * An Abundance of Katherines: Maybe not every week, but Colin has dated more girls named Katherine than he's had years in his life.
 * Gossip Girl has two. Nate Archibald and Serena van der Woodsen.
 * In some of the Dragonlance Novels detailing the early lives of the Heroes of the Lance, Caramon is described this way. His brother makes some snarky remarks about his tendency to be in love with a new girl every week, though eventually he settles down with his true love Tika.
 * Adolin from The Stormlight Archive is this in spades. Frequently lampshaded by his brother, and several other characters.
 * Claire Stanfield from Baccano has a history of this, literally falling in love and proposing marriage to complete strangers, almost at random. He has a hard time convincing his brothers that his relationship with is any different other than that she didn't immediately say no.
 * In Will Grayson Will Grayson Tiny Cooper is constantly swooning after and being heart-broken over guy after guy (after guy after guy). Apart from his gay-ness and large-ness, this is practically his defining feature.
 * Howl from Howl's Moving Castle pretty much defines this trope. He goes out, falls in love with a girl, spends an inordinate amount of time and effort wooing her, and then...drops her once she falls in love with him. Repeat on infinite. The first one he fails to do this to is Sophie, who turned him into a Ladykiller in Love and who he eventually married.
 * Bingo Little from PG Wodehouse's Jeeves and Wooster series, . Bertie himself could count as a milder example--he falls for one Girl of the Week after another, but generally ends up expressing relief when things don't work out.

Live Action TV

 * Bingo Little from Jeeves and Wooster, in the show's first three episodes alone, is "in love" with four different girls!
 * Ted Mosby from How I Met Your Mother realizes that the odds of the next girl he's interested in being The One are pretty dismal. It doesn't stop him from trying.
 * Lampshaded in a recent episode when Lily complains about all these random girls showing up in their group photos.
 * Izzie from Greys Anatomy is a female version. Her "true loves" include her patient Denny Duquette, George, and Alex.

Theatre

 * The Trope Namer is Romeo from Romeo and Juliet, who is himself something of a Serial Romeo. At the beginning of the play he is desperately in love with a girl named Rosaline, who has rejected him. Soon after, he meets Juliet, and promptly forgets his feelings for Rosaline, which he now sees as a passing infatuation. Goodness only knows how many more times he would have gone through this had Juliet also rejected him.

Video Games

 * Larry Butz from the Ace Attorney series is constantly either trying to get together with a woman with whom he's fallen madly in love, or just been dumped. We rarely see him actually in a relationship. This is a big part of his character, though: He also has a different job every time we see him.
 * Jenon of Blaze Union, at least from the way Garlot immediately groans and goes "well, here we go again" when he falls for Medoute.
 * A series of sidequests in Strange Journey involves the player character delivering love messages for a crewman named Anthony, who falls in love with a succession of female demons. And the first few times, the music cuts out when Anthony confesses this fact. Eventually, Anthony grows up a little, and the last of these quests has him ask you to look up a goddess of love for advice on how to talk to human girls.

Web Original

 * Rosethorn, of the Whateley Universe, whose first name really is Romeo. He's strikingly handsome, and has mutant powers. He tends to find Miss Right, make her over, improve her self-esteem, etc., until she dumps him. She always dumps him. Either she hates being the dumpy one in the relationship, or she becomes 'pretty' enough for other guys to see her as desirable, or the whole 'my mother is a dangerous supervillain' thing comes up and torpedoes the relationship, or...
 * Although the Lord of Angels and Demons (of The Questport Chronicles) is treated as The Casanova in-universe, he's actually more this trope, especially with regards to the Secret Keeper and the Queen of Rogues and Robbers.

Western Animation

 * A female version from 6teen is Caitlin.
 * Johnny Bravo.