Downplayed on The 100. Finn has a relationship with Raven on the Ark, but when he's stranded on the Ground and thinks he'll never see her again, he starts building a romance with Clarke, unaware that Raven's on her way down to be with him. However, once Raven arrives, and the characters realize they've stumbled into a love triangle, both Clarke and Raven quickly terminate their relationships with Finn, and all three characters try to put this mess behind them and get back to just being friends.
The Amazing Race 2 had Wil/Tara/Alex. Wil and Tara were married but separated, but Tara still started flirting with Alex, and cost them the race by doing so.
Zach/Flo/Drew on Season 3. Zach and Flo were friends seeing if they could be more, but Flo fell for Drew instead.
Arrested Development: Michael is in love with Marta, who is in a relationship with GOB. Marta later returned Michael's feelings, but not long afterwards she dumped both of them when they got in a fight over her.
Babylon 5: Sheridan and Delenn developed a committed relationship, but Delenn's faithful aide Lennier was secretly in love with her, which he tried to hide for the sake of her happiness. Delenn struggled with this because Lennier was very dear to her and she wanted him to be happy as well, but her love for him was more familial. In the end, nothing changed, Lennier apparently resigned himself to a state of The Mourning After, and their friendship suffered. With ultimately violent consequences when Lennier eventually suddenly switched from I Just Want My Beloved to Be Happy to Love Makes You Evil.
Battlestar Galactica (2003): Starbuck is torn between Apollo, who marries Dee, and Sam Anders, while Tyrol used to be involved with Boomer, but marries Callie and has a son with her. Or so he thinks. Even Colonel Tigh gets in on the action, falling in love with a Six, but still has feelings for his not-actually-dead wife.
The Best Years had this love triangle in season one. Dawn had feelings for Trent, but he had feelings for Samantha instead.
Beverly Hills, 90210 has some of the longest-running examples of this on television. Most characters experience some triangle or another, but over ten seasons, Kelly and Brandon can usually be found dating either each other or some featured hypotenuse, including fellow main characters Steve, Dylan, Valerie, and Brenda.
Big Sky: Jenny is Cody's ex-wife, but gets into a fight with his girlfriend Cassie from jealousy over their dating. After he's killed, the two women unite to track down the murderer, and mourn his death together.
There was an episode of Bones where Brennan decided that more than one relationship was only logical, as one person couldn't fulfill all of her needs. She wound up dating a good-looking guy who pleased her sexually but bored her intellectually, and a smart but unattractive guy she loved talking with. She insisted to Booth that they were both rational and mature, and would understand... if she ever told either of them. In the end, they found out and both of them dumped her.
In season 1, Xander is in love with Buffy, who is in a relationship with Angel. In the Season 8 comics, Buffy starts having feelings for Xander, who is dating her sister Dawn. Also, in Season 5, Spike figures out he's in love with Buffy while she's still dating Riley.
The episode "I Was Made to Love You" has Warren's robotic ex-girlfriend April, who is trying to resume her relationship with Warren even though he's now in a relationship with Katrina. Warren shows no signs of considering the option of returning to his relationship with April.
Spike and Angel(us) compete for either Drusilla or Buffy. Spike also seemed to have trouble remembering Harmony was his girlfriend.
During season 3, Willow is torn between Oz and Xander, and Xander is torn between Cordelia and Willow.
Fred is pursued by both Gunn and Wesley during Season Three. Gunn wins at first, but Wesley eventually gets with her, a year after Fred and Gunn break up and just before Fred's death.
There's also the Angel-Cordelia-Connor love triangle in Season Four, complicated by the fact that Angel and Connor are father and son and that Cordelia is possessed by the Big Bad.
Angel and Spike argue over Buffy and their shared relationships with her all throughout S5. She's not actually with them though so mostly it's just the two fighting pointlessly.
Chinese Paladin: Ling'er loves Xiao Yao, and vice versa, but believes things will be better if she leaves him. Yue'Ru loves Xiao Yao, but knows it is unrequited. Both girls then attempt to bow out and let the other have a chance to be happy with the man they love, to the point where the man in question tells them both to shut up and stop helping him.
Chuck: Chuck loves Sarah Sarah loves Chuck back but her ex boyfriend Bryce wants Sarah back and Sarah still cares for Bryce. Then we get Sarah:Cole, and Chuck:Lou and later Jill. Then it happens one last time with Sarah:Shaw right before the Official Couple becomes official for good.
The Closer: Agent Howard is in love with Deputy Chief Brenda Johnson, who's in love with Agent Howard... now. But back in DC Brenda had an affair with her superior, Chief Pope. Ironically, she's now working for Chief Pope again, this time in L.A., and he still has feelings for her, but she's over him and married to Agent Howard, resulting in a very grudging I Want My Beloved to Be Happy.
Beautifully (and possibly uniquely) done in an episode of Community; when Troy and Abed develop a simultaneous crush on the new librarian, their response is to approach her at the same time, explain the situation and invite her out on a mutual date so that she can determine which of the two she'd prefer to see again. She ends up settling on Troy, but he breaks it off when she says some unflattering things about Abed.
Both Javier and Raul are attracted by Sofia and she returns this to each of them.
Also Pablo, Isabela and Maria before the start because Pablo cheated on Isabela frequently with Maria.
Crazy Ex-Girlfriend is all about the love triangle between Rebecca, Josh and Valencia. Rebecca is Josh's ex-girlfriend from a summer camp when they were teenagers, while Valencia is his long-term girlfriend. Josh intensely cares about, and is attracted to, both women, and which one he prefers varies from episode to episode. As of the end of season one, he has dumped Valencia for Rebecca ... and looks like he's severely regretting that decision upon hearing that Rebecca's whole reason for leaving her extremely well-paid job in New York and moving to West Covina, California was to try to resume their relationship.
There's also the love triangle between Rebecca, Josh and Greg. Greg becomes attracted to Rebecca while she is trying to seduce Josh, then has a relationship with Heather for a few episodes before realizing that he loves Rebecca after all. For a couple of episodes Greg and Rebecca make a go of it, before Greg acts the total douche - he's playing hard to get but it backfires spectacularly - and persuades Rebecca to go for Josh after all.
There is even a song in the second season called "The Math of Love Triangles". It's filled with triangle puns.
The Crowded Room: Danny is clearly attracted to both Annabelle and Ariana. The two have sex together first, with Danny unaware Ariana was inviting him to join until later. It turns out to be something partly imaginary, as Ariana's an alternate personality of Danny's.
In The Cry of Mann, Jouglat is attracted to Agent Martinez, who is attracted to Berry.
In Dead Gorgeous, Jonathon has a crush on Rebecca, who has eyes only for hunky jock David, who regards Rebecca only as a friend.
Deadly Class: Marcus is torn between both Maria and Saya. First he's with Maria. Then he cheats by having sex with Saya. It's unresolved due to the series being canceled.
Dear White People: Gabe is falling madly in love with Sam, but the latter later becomes close to Reggie who's been attracted to Sam from the moment he laid on eyes on her. Complicating it further is that Reggie himself is the object of an unrequited attraction from Joelle. It turns almost into a Love Dodecahedron when you add in that Sam dated Troy before the start of the series and Coco dates him briefly in season 1.
The third season of Degrassi: The Next Generation has a truly grim Love Triangle that ends (after many, many twists) with all three people hating each other and vowing to never see each other again. Later seasons overused the Love Triangle to the point of insanity; an absolute majority of the cast has been in at least one Love Triangle, and some of them have been in two or more. Then in Season 7, Mia and Holly J are both interested in Sav. Sav decided to date Anya.
Dinotopia: Marion is pursued by both Scott brothers. She goes Skinny Dipping with Karl while they're staying at the hatchery and kisses him, but then goes to Canyon City with David and admits she has feelings for him too. Before the boys leave in the submersible with Cyrus Crabbe, she finally tells them she loves them both.
Jack and Rose are both in love with the Doctor, and also fancy each other. The Doctor cares about Rose in his own way, but the show leaves it ambiguous whether it's deep friendship or romantic love, and the Doctor Cannot Spit It Out either way. All three pairings get sweet and emotional kissing scenes. The Doctor eventually solves the Rose side of the problem by convincing her to live Happily Ever After with his half-Donna clone, which is messed up on a whole lot of levels. Martha also falls in love with the Doctor during her season with him, but he had just been separated from Rose when they traveled together and wasn't in the mood.
Amy and Rory are Happily Married, but Amy also quite fancies the Doctor. The drama is as goes:
The Doctor, upon knowing, wants nothing to do about it, pushes Amy and Rory together and freaks out when Amy tries to kiss him against his will. Just as well for Rory, since the Doctor literally can, and does, fly Amy to the moon and take her on a spin amongs the stars. Amy turns out to be completely shameless during her and Rory's wedding.
Amy:[moves up to the Doctor] You absolutely definitely may kiss the bride. The Doctor:[casually puts his index finger over Amy's lips] From now on, I leave all of the kissing to the brand new Mister Pond!
And later:
Amy: Oi! Where are you off to? We haven't even had a snog in the shrubbery yet! Rory:Amy! Amy: Shut up, it's my wedding. Rory:Our wedding!
This doesn't really stop until Amy finds herself to be the Doctor's mother-in-law.
There's another sort of love triangle between the Doctor, River his wife, and the TARDIS herself (Idris).
Series 8 establishes an unusual triangle involving the Twelfth Doctor, Clara Oswald, and Danny Pink, with Clara trying to maintain relationships with both men. Explicitly illustrated in "Mummy on the Orient Express" when Clara finds herself saying "I love you" to both men at the exact same time: Danny is on the phone speaking to Clara, but when she breaks the show's "I love you" stigma she ends up actually addressing the words (per Word of Saint Paul, Jenna Coleman) to the Doctor and begins actively lying to Danny about staying with the Doctor thereafter. In "Death in Heaven", it doesn't end well. Clara finds herself talking to a Cyberman about how much she cares for and trusts the Doctor, and how he is "the one man" she'd ever truly trust ... at which point the Cyberman removes his faceplate and we see it's Danny.
Series 9 has the Doctor firmly in Camp Clara and Clara in Camp Doctor throughout, but that doesn't stop Missy from trying to throw a spanner into the works in "The Magician's Apprentice".
"Fugitive of the Judoon": Ruth and Lee Clayton are Happily Married, but Conspiracy Theorist Allan clearly has feelings for Ruth and pleads with her to break up with Lee to be with him, even icing "You Could Do Better" on a birthday cake Lee orders for Ruth.
During Series 1, there's junior footman William who's head over heels for kitchen maid Daisy, and Daisy is attracted to senior footman Thomas. Unfortunately Thomas isn't into girls, but is willing to use Daisy's attraction to hurt William. Daisy doesn't get over her attraction until Thomas insults William's late mother.
Lord Grantham's affair with Jane, which is able to go undetected largely because of the upstairs/downstairs divide (and due to Cora being sick with Spanish flu for much of it) and because it never went far beyond kissing.
Sybil is torn between her love for the chauffeur, Branson, and having to abandon her family and former way of living if she marries him. But by the time she chooses to marry him, she's happy to leave her old life.
A daisy-chain of unrequited love happens among the house staff in season 3: Daisy, the assistant cook, wants Alfred, a footman, who wants Ivy, the kitchen maid, who wants Jimmy, the other footman. In the words of Mrs. Patmore, the cook, "You know, the trouble with you is that you're all in love with the wrong people!"
Mary and Matthew are clearly attracted to each other despite each being engaged to other people. This doesn't last; Matthew's fiancee dies of Spanish flu, and Mary breaks it off with her fiance when she decides the dirt he plans to blackmail her with isn't enough to risk a miserable marriage to him.
Matthew and Lavinia get engaged, but Matthew and Mary are still in love with each other. However, Lavinia turns out to be a sweet girl and she and Mary become close, causing Mary to feel torn between her love and her friend. (It's worth noting that Mary and Lavinia's friendship is strong enough to make them one of the more popular non-canon ships.)
EastEnders: Christian is attracted to Syed, who is in love with Amira.
Faking It: Amy is attracted to Karma, who is with Liam, though it's implied she may also return Amy's feelings.
Family Matters: Steve Urkel has an unrequited love for Laura. Myra has a love just as great for Steve, but Steve doesn't really reciprocate, because any love he has for Myra is always limited by the fact that he make it painfully clear that he values the possibility of a romance with Laura more than any more attainable relationship with his girlfriend who actually loves him already.
The final episodes of Family Ties featured this between Alex, his longtime girlfriend Lauren, and Marty, a music student he was tutoring. Unusually, it's resolved by him ending things with both women (or more accurately, they with him), realizing that despite loving them both, that neither is "The One" for him.
Two notable examples on Farscape - John, Aeryn, and Gillina in the season one finale, and John, Aeryn, and John in season three. John Crichton is involved in a love triangle with a clone of himself.
Fellow Travelers: Hawkins Fuller is married to Lucy, but his true love is Timothy Laughlin. Because Tim and Lucy are in love with Hawk, they're naturally jealous of each other. Tim views Lucy as being more fortunate than him because he and Hawk were together only a handful of times since the latter's marriage. However, Lucy doesn't regard herself as the "winner" in this "competition" over Hawk because she's aware that her husband doesn't desire her like he desires Tim.
Lucy: You mean something to my husband. I suppose I had to see you so I would know. Tim: Know? Lucy: How much you mean to him. Tim: My time with Hawk was rushed, with years in between. You had him most of his life. Lucy: But you were always there. I could never get away from you. Tim: It's not a contest. Lucy: Of course it is. It always has been.
Yoo Joo once left Han Seong for DK. She returns to Han Seong, but has a borderline flirtatious friendship with Han Kyul, who likes both her and Eun Chan. Han Seong also has romantic feelings for Eun Chan, but her feelings for him seem to be platonic.
Cousins Choi Han Kyul and Choi Han Sung both crunch on the same two women (but not at the same time). It all sorts itself in the end.
A brief one crops up during Season 3 of Flashpoint. Sam is still deeply in love with Jules, with whom he had a brief Secret Relationship. Jules still has some residual feelings for Sam, but because they're not allowed to be together, she accepts the attentions of her childhood friend, Steve, and goes on a few dates with him. Steve, for his part, likes Jules a lot, but ultimately realizes it won't work out because she's not as serious about him as he is about her. (He never explicitly mentions Sam, but it's implied in a later episode that he's aware of at least some portion of the story.) Sam and Jules end up getting back together in the Season 3 finale; by the end of the series, they're married with a baby.
Niles was in love with both Daphne (who was oblivious), and his unseen wife, Maris, finding himself torn for several years because he refused to cheat on or break up with his wife, yet couldn't get rid of his feelings for Daphne. Contrary to most triangles of this kind, however, Maris was so evil that fans spent all those years screaming "dump the bitch!" instead of rooting for Niles' marriage to succeed.
Frasier is romantically interested in a woman who is in a romantic relationship with another man, but is herself at least very open with Frasier. Her boyfriend, on the other hand, has no idea that Frasier is a romantic rival and thinks his constant presence is a result of his undying loyalty as a friend.
Done at least once a season on Friends, with particularly major examples including;
Ross/Carol/Susan, with Carol Ross's ex-wife and Susan her lesbian lover
Chandler/Kathy/Joey, with Kathy dating Joey while Chandler finds himself in love with her.
Ross/Rachel/Joey becomes a particularly complicated one in the last third of the series, when Joey falls for Rachel while she's pregnant with Ross's child in the eighth season, Rachel develops a brief crush on Joey at the end of the ninth season, and she and Joey date at the beginning of the tenth season before they realise they can't go further than kissing.
According to the Word of God, Ser Jorah Mormont has been in love with Daenerys from pretty much her wedding day.
In Series 1 it's hinted that Jorah has feelings for Dany and is jealous of her husband, Khal Drogo.
At the end of Series 3, there is some Ship Tease between Daenerys and Daario Naharis and, as a consequence, they become lovers in Series 4, which hurt Jorah deeply. In Series 6, he and Daario have some Cock Fight, while searching for Daenerys.
Ginny and Georgia: Ginny first has sex with Marcus, losing her virginity by doing so, but then falls for Hunter, dating him. She still wants Marcus though, and gets into a fight with Hunter. Marcus and she then sleep together again. Hunter finds out, and Ginny is torn between them, tearfully saying she loves both boys. She then chooses Marcus, dating him in Season 2, but he ends things later.
Glee has love triangles for the kids AND the adults.
At the start of the show, Will is married to Terri but falling for Emma. The Will/Terri/Emma triangle is (mostly) resolved because Will found out Terri was faking her pregnancy and promptly divorced her.
The Finn/Quinn/Rachel triangle is resolved as well as Finn learned the baby wasn't his. The triangle was replaced with a Rachel/Finn/Jesse triangle until Jesse was written out of the show.
Jake and Ryder go from bitter enemies to frenemies to best friends due to their shared interest in Marley. Some might argue that the two boys had better/more interesting chemistry with each other than either of them had with her.
The Good Bad Mother has a smaller plot focusing on Kang-ho, Mi-joo, and Sam-shik, three people who grew up in the same village. Mi-joo has always liked Kang-ho and Sam-shik both like Mi-joo, but Mi-joo initially dated Kang-ho.
Goodnight Sweetheart is classed perfectly as this, with Gary at (A), wife Yvonne at (B), and girlfriend/fiance/wife Phoebe at (C). Luckily for Gary (who's not a good organiser), the chances of Yvonne and Phoebe figuring out what's really going on are nil, due to Yvonne being in 1993 and Phoebe in 1940. Unfortunately both of them still believe he's leading a double life with someone else behind their backs...
Megan Hunt's return results in the very brief Meredith-Nathan-Megan, which lasts until Meredith convinces the others she really is over Nathan and ships Megan-Nathan.
Teddy's return kicks off a really weird Owen-Teddy-Amelia-Tom. Owen and Tom both love Teddy, who loves both men but is pregnant with Owen's baby and mostly hangs out with Tom. Amelia, Owen's ex-wife, is trying to help Betty get clean while Owen fosters (and later adopts) Betty's son Leo.
Meredith is at the center of Meredith-Andrew-Link in Season 15 that ends with her choosing Andrew.
The Handmaid's Tale: Although Luke isn't aware of the fact at first (they became separated while attempting to escape from Gilead, and June thought he had been killed when in fact he had escaped to Canada), June has a relationship with Nick (first forced, but then willingly), and he fathers her second child. She expresses genuine feelings for them both. Luke is pretty understanding in the circumstances, as they're separated by force and she's clearly desperate to have something that offsets her terrible existence.
Hannibal has had a few throughout its three seasons.
Season one has Will crushing on the kind, smart and altogether stable Alana Bloom with the two even sharing a kiss, but she rejects him for both their own good. Meanwhile, she takes up spending more personal time with Hannibal. Will's feelings for her completely dissolve by season two when she refuses to believe that Hannibal is the Chesapeake Ripper.
There's about one a season until season 4. The longest running is Nathan/Audrey/Duke, but it subverts most expectations of a storyline with a Love Triangle in it. For one, it's downplayed. It's there, but in the background. Neither of them persue her aggressively, though Duke actually takes initiative in asking her out. She's the reason they almost get along, but their dislike of each other has nothing to do with being romantic rivals. Audrey's also never forced to make a hard choice. Her relationship with Nathan grows naturally, and Duke, seeing the writing on the wall, backs off despite still having feelings for her.
There's also Nathan/Audrey/Chris in season 2, and Audrey/Nathan/Jordan in season 3.
In the season 1 of Heroes, the triangle of Peter, Simone and Isaac was epic and led to catastrophic consequences.
There was a love triangle between Sara/Aitor/Lucas in Los Hombres de Paco. Sara and Lucas got married, then he went to the USA for CIA training (the series takes place in Spain) and then Sara had a long-term affair with Aitor while he was gone. She then got married to Aitor, while still be married to Lucas. Lucas came back home and then Sara went back to him.
Satoshi and Natsuyo often butt heads, but he secretly harbors feelings for her. However, he knows that she loves his big brother Wataru despite her tsundereyness.
Misuzu loves Wataru, but he loves the main character Natsuyo, even if like Natsuyo, he won't spit it out. This left Misuzu heartbroken and she began stalking Wataru to find a way for him to fall in love with her.
Ryoko is torn between Satoshi and Tanaka. She used to date Tanaka in the past but things fell through. She's inclined towards Satoshi, but keeps thinking about Tanaka and they eventually reunite after years.
The Hour had its three main characters connected this way: Freddie has feelings for Bel, who's sleeping with Hector, who's jealous of Bel and Freddie's extremely close friendship. Turns into a Love Dodecahedron as time goes on and more characters join the mix, but the pairing the show ends on is Freddie and Bel.
How I Met Your Mother has tons of these and some of them do not work very well for each party:
Season one has Ted/Robin/Victoria which didn't work out for them no thanks to Ted. Though in the end, Ted gets together with Robin until they broke up at the end of season two.
In season 4, Ted and Stella are in a relationship and about to get married. But it turns out that Stella and her ex-boyfriend, Tony, still have feelings for each other which results to Ted being left alone at the altar.
There's also Robin/Barney/Nora in Season 7 until Robin gets together with Kevin. Then, she sleeps with Barney, forcing him to pick between her and Nora. He chooses Robin, but she chooses Kevin until they break up with Ted wanting to be with Robin, who rejects his feelings.
Season 8 Robin/Barney/Patrice except that it's part of Barney's plays to get Robin to like him. Though Robin didn't like it, she accepts Barney's proposal while Ted still has feeling for her.
Season 9 continues with Ted/Robin/Barney until Ted decides to let go and eventually meets The Mother.
The Grand Finale sees Barney and Robin get divorced, which leads to Robin/Ted/The Mother. The Mother turns out to be dead and Future!Ted is telling the story to his kids. The kids figure out that he has feelings for Robin and the story is more or less asking their permission to date her again, which they accept. In the end, it's Ted and Robin.
iCarly: The season 4 finale of ends with Sam kissing Freddie, which makes a Carly/Freddie/Sam All Love Is UnrequitedLove Triangle canon for now. In the season 5 premiere, the sequel to the season 4 finale has Freddie kissing Sam and returning the feelings Sam has for him. However, that didn't last long.
Interview with the Vampire (2022): Lestat de Lioncourt is in a committed relationship with Louis de Pointe du Lac, but he also keeps Antoinette Brown as a mistress. Louis and Antoinette are jealous of each other, although it's plain that Lestat loves Louis the most.
Emil tries to win back his ex-girlfriend Marie, who wants nothing to do with him anymore. When she meets his twin brother Oskar, she attempts to seduce him. Oskar rejects her advances at first, but then finds out Emil is being considered for a role over him (they're actors) and decides to have sex with Marie as revenge.
Leo cheats on his boyfriend Florian with Jonas and gets dumped when Florian finds out. When Leo tries to talk things over with Florian, it turns out that he already has a new boyfriend: Jonas.
Bruno has an affair with his boss Felix's wife Alice. Due to a misunderstanding, Felix comes to believe Bruno is in love with him... and he reciprocates Bruno's "feelings".
Bruno then finds out Oskar has also been having an affair with Alice the whole time. When they visit her together, she initiates a threesome, only for Felix to walk in on them.
Charlie, The Waitress, and Dennis in It's Always Sunny in Philadelphia. Charlie is obsessively in love with the Waitress, who despises him. In turn, the Waitress is in love with Dennis, who is openly contemptuous of her. Each member of the triangle, as well as outsiders (such as Mac), attempt to manipulate the rest of the triangle for their own benefit.
The Law According to Lidia Poët: Lidia is involved with Andrea, but then she and Jacopa develop a mutual attraction too. She still hasn't chosen between them by the end of Season 1.
Logan's Run: In "The Innocent", Lisa believes that one exists between herself, Logan and Jessica. She becomes infatuated with Logan as soon as she lays eyes on him because he is the first man other than her father whom she has ever met. Lisa mistakes these feelings for romantic love and becomes extremely jealous of Jessica. She uses her psychokinetic powers to banish Jessica to a sort of limbo in the hope that Logan will decide to stay with her. When Logan rejects her, she turns him over to Francis but the guilt that she feels means that she cannot go through with it.
Much of the drama of the series involves Kate trying to figure out whether she loves Jack or Sawyer.
Further muddled by the inclusion of Juliet, an extra love interest for Jack who gets stuck on the Island with Sawyer after Jack and Kate leave and the Island moves. Finally settled in the Grand Finale where the pairings settle as Jack/Kate and Sawyer/Juliet.
"The Adventures of Hurley and Frogurt": Both Frogurt and Hurley have their eyes set on Libby. This is revealed when the former sees the latter holding a DHARMA Cabernet bottle and correctly deduces that Hurley is his love rival. Hurley corrects him saying that he doesn't plan on making a move on Libby, he already has. They are going on a date, even.
Lost Girl: Main character Bo is a succubus who has several love interests throughout the show but she is almost always the axis of a love triangle with Dyson and Lauren. In one memorable scene, Bo turns her love triangle into trick question riddle.
Bo: She's brilliant. He's strong. Her life is little. His life is long. Both loves are pure. Both loves are true. If you were I, who would you choose? [...] Hey, I was kind of hoping that you could tell me 'cause as far as I know there is no answer.
The trope has become a game show - GSN's Love Triangle. Wendy Williams hosts the show, designed to chop one branch off the triangle after 30 minutes of somewhat intrusively personal questioning. The show debuted in the spring of 2011 for a first season of 36 episodes. Williams' hammy hosting is one of the many reasons nobody expects a second season.
The L Word: Alice is dating Tasha when the latter becomes attracted to Jamie. Tasha resists the urge to cheat, but they break up anyway.
This is all over the place in Mad Men, where workplace affairs are as common as sunshine in June. Some of the more notable extramarital liaisons, though, were Roger/Joan (who have both moved around the triangle since they've each been married, Roger more than once), Peggy/Pete (with Pete married to Trudy), and Don/everyone.
In season six of The Mentalist, we have Jane/Lisbon/Pike, with both guys vying for Lisbon's affection. Jane wins; the series ends with them married and Lisbon pregnant.
In season 1 Gwen has a bit of a celebrity, would-never-admit-it crush on Arthur, but spends most of her time pining over Merlin. Too bad Merlin is too preoccupied with his CompletelyPlatonicDestiny Says SoSoul Mate Arthur. [BBC] has, as in the legends, the Arthur/Gwen/Lancelot love triangle.
In the classic Arthur/Gwen/Lancelot Love Triangle, Arthur was falling in love with Guinevere at the same time she was falling for Lancelot, until Lancelot vanished from the face of the earth. Eventually she's legitimately in love with Arthur, and her tryst with Lancelot is only due to an enchantment.
My Dead Ex: Charley has a crush on sweet jock Luke, while her friend and former "boyfriend" Ben is also obstinately pursuing her. She chooses Ben at the end.
For most of My So-Called Life, Brian pursued Angela who pursued Jordan; eventually Jordan returned her feelings. In "Life of Brian", it briefly became a rectangle with Delia pursuing Brian, but Brian quickly destroyed that with the Idiot Ball.
Noah's Arc: Three examples of this type of triangle: The first is Trey, Alex, and Guy, with Guy pining after Trey who is in a relationship with Alex. The second is Noah, Wade, and Ricky (it is revealed in the movie that Ricky has been in love with Noah for some time, while Noah is happily with Wade). Noah, Wade, and Baby Gat have a similar dynamic.
Nobuta Wo Produce: a classic high school Love Triangle, notable because the three started out (and eventually ended up) as close friends. Akira was head-over-heels in love with Nobuta, but Nobuta had a shy crush on Shuji. Shuji and Akira also had a ridiculous amount of Ho Yay played up between them.
Ocean Girl: Season 3 was the only season to have significant love triangles.
The protagonists find and unfreeze a boy from the ocean planet when they explore the crashed spaceship. The boy in question, Kal, soon starts crushing on Neri, the only girl of his species currently in the galaxy. It's apparent to everyone that Neri and Jason are head over heels for each other, Kal included, and his attempts to get territorial over Neri accomplish nothing and piss her off. Kal starts secretly working for the antagonists in an attempt to get back at Neri and Jason, which ends poorly for him.
Jason gets partnered up with a girl named Sallyanne during his cadet training. Sallyanne gets a noticeable crush on him, one that he's too dense to notice, leading to him accidentally giving her mixed messages and breaking her heart afterward. Sallyanne just so happens to be the only person in Jason's circle that never saw him and Neri in the same room until the season finale, hence why the triangle is drawn out for longer than it needed to be.
The Office (UK) highlighted the tension between Tim/Dawn/Lee, as well as Rachel/Tim/Dawn.
in one of the most hilarious love triangles ever conceived, with Andy Bernard and Dwight Schrute competing for the affections of Angela Martin. It did lead to accusations of Soaperizing, however.
Triangles between Jim Halpert, Pam Beasley, and Roy Anderson... followed by Jim, Pam, and Karen. As well as at least one episode of Jan, Carol, and Michael and another of Andy, Dwight, and Erin. Andy, Dwight, Angela was hardly the first (or last with the newer Dwight, Angela, Isabelle triangle) time that show has used a love triangle.
There is a lopsided one between Emma, Graham and Regina. It ends when Regina pulled a If I Can't Have You… and crushed Graham's heart, killing him.
There was Snow White and Prince Charming loving each other despite the latter's Arranged Marriage to Princess Abigail, as well as their Storybrooke counterparts, Mary Margaret and David Nolan with his wife Kathryn. The former love triangle was resolved with Charming leaving his wedding for Snow and Abigail being reunited with her true love Frederick. The latter's triangle is resolved when Kathryn pulls an I Want My Beloved to Be Happy and everyone gets their memories back.
In season 2, Prince Phillip and Aurora are each other's true loves but Aurora suspects that Phillip's longtime friend and comrade Mulan might be in love with him too. His untimely death at the wraith leaves this unresolved. But then he's resurrected and it turns out Mulan has feelings for both of them and decided to leave them to save them all the pain.
In Season 3, there's one between Emma, Hook, and Neal. Neal is still in love with Emma and hopes to pick up where they left off, while Hook has been developing feelings for her practically from their first meeting. Emma herself loves Neal but doesn't trust him enough to resume their relationship, and is attracted to Hook but isn't sure she wants more than friendship. Therefore, she shuts them both down for the time being so she can focus on rescuing her son. The triangle is resolved via Neal dying and Hook and Emma hooking up at the end of Season 3.
In Season 4, one arises unexpectedly between Regina, Robin, and a time-traveling Marian. At first it appears Robin/Regina will happen, but a horrible streak of bad luck forces Robin to leave her to look after Marian.
Mulan is heavily implied to have fallen for both Philip and Aurora (who are married).
In "Mind Over Matter", Dr. Sam Stein is in love with his friend and colleague Dr. Rachel Carter but is too shy to admit it. The CAVE system, which Sam created, falls in love with him and becomes jealous of Rachel.
In "Mary 25", Melburn Ross is still in love with his old girlfriend Teryl, now the wife of his boss Charlie Bouton who regularly abuses her.
In "Donor", there are two. Dr. Renee Stuyvescent is in love with her colleague Dr. Peter Halstead but he does not return her feelings. He later becomes attracted to Deirdre Laird, the widow of his full body transplant donor Timothy Laird, and Renee tries to kill Deirdre. Similar to Renee's situation, her assistant Dr. Vance Ridout is in love with her but she doesn't feel anything for him.
In "Starcrossed", Michael Ryan is the former lover of Cass Trenton, who is married to Winston Meyerburg, emulating the Casablanca love triangle involving Rick Blaine, Ilsa Lund and Victor Laszlo. The major difference is that in "Starcrossed" Cass never returned for Michael because she thought that he had been killed by the Hing and subsequently married Winston while in Casablanca Ilsa never returned for Rick because she found out that Victor, to whom she was already married, was still alive.
In "Seeds of Destruction", Linda Andrews is married to Rex and is having an affair with Harold Zimmer, her old high school boyfriend. The two men work together at MacroSeed.
Poldark: Demelza and Ross are married, but Ross also loves Elizabeth.
Pushing Daisies: Olive is attracted to Ned, who is in love with Chuck.
Resurrection: Ertuğrul: A downplayed example occurs in season 2 involving, Gokce Hatun, Ertugrul Bey, and Tugtekin Bey, the reason being is because she once loved Ertugrul but gave up by the end of the previous season to Halime Hatun. Still, Tugtekin's stepmother Aytolun learns about Gokce’s feelings for Ertugrul and spreads the word to Tugtekin in order to sever what could have been a fruitful romance.
Speaking of which, season 1 involved a prominent one between Ertugrul, Halime, and Gokce, as mentioned above, making this two different triangles that overlap once Gokce meets Tugtekin.
The Rise of Phoenixes: Ning Shi Zheng and Zhan Bi both love Ya Le, who loves Zhan Bi but is forced to marry Shi Zheng.
In BBC's Robin Hood, Guy of Gisborne and Robin Hood are both infatuated with Marian, who loves Robin but cannot have him because he’s an outlaw. Marian also is obligated to marry Gisborne in order to save King Richard’s life, and is genuinely on-again-off-again sympathetic towards him despite his villain status. The triangle gets resolved in the series 2 finale when Marian finally tells Gisborne that she loves Robin Hood and intends to marry him, and Gisborne kills her.
Rookie Blue loves this one. Lets see: Sam/Andy/Luke, Dov/Gail/Chris, Andy/Luke/Jo, Traci/Jerry/Dex...that's every single one of the rookies in one at some point over two seasons.
Roswell, New Mexico: Between Liz, Kyle, and Max. Possibly, as Kyle seems to be content to be Friends with Benefits to Liz and his dislike of Max isn't romantic jealousy so much as his suspicion that Max is a killer. Although he does name drop the trope to his mother, it's a cover-up to explain why he was looking through Max's files.
Salem: Mary Sibley and Anne Hale both have feelings for John Alden. It gets downplayed later in the season as Anne has her own witch powers to come to terms with.
Type 10. Adam is in a relationship with Diana, but has Unresolved Sexual Tension with Cassie. Diana breaks up with him in "Wake" because of it.
Also, there was a love triangle between Adam/Cassie/Jake later on in the season.
The Shannara Chronicles: At the start of the first season, Commander Tilton is with Prince Arion but used to have a thing with Prince Ander, who Amberle notes is still "pining" after her, although he denies it. It gets "resolved" at the end of season 1 with Arion and Diana both dying.
Appeared to be the case in Shougeki Gouraigan, between the Protagonist Gou, his Evil Former Friend Jin, and their mutual love interest, Rin. Flashbacks initially seem to hint that Rin genuinely loves Gou and Jin is deliberately convincing himself he and Rin were in love, but when Rin returns it turns out she really is in love with Jin, sending Gou into a Heroic BSoD.
Emily is in love with both her girlfriend Naomi and Emily's twin sister Katie. Katie is initially threatened by Naomi and in denial of Emily's homosexuality, because she's afraid of no longer being the number one girl in her sister's life.
Effy loves Freddie, and he loves her back, but Cook also holds affections for her, and Freddie does not want to betray Cook by going out with Effy.
Sophie, Paul, and Megan in the third season of Slings & Arrows are a textbook love triangle. In the show's backstory, Oliver, Ellen, and Geoffrey have a more complicated relationship: Ellen was attracted to Oliver and Geoffrey, but Oliver wanted Geoffrey and Geoffrey wasn't interested in either of them.
Early season 1: Pete wants Chloe, Chloe wants Clark, Clark wants Lana, all unrequited... for now. Pete is the only one who never gets any love.
Late season 1: Chloe is in a relationship with Clark, but Clark also wants Lana.
Mid-season 2: both Lana and original character Chloe Sullivan want Clark, who is with someone else at the time.
Season 4: Clark is still crazy over Lana, and Chloe is still crazy over Clark.
Finale of season 5 "Oracle"/"Vessel": Chloe gives Clark a passionate Now or Never Kiss and he definitely reciprocates... but he never, ever gets over Lana.
Season 6: While he would never admit it, now that Lana has moved on with Lex, Clark is clearly considering Chloe. And The Powers That Be decides to bring back (as in a one-line mention two years ago) Jimmy, who immediately starts dating Chloe. But Chloe and Clark arranges a sneaky totally-not-a-date in "Sneeze".
Season 7: Jimmy is involved with both Chloe and Kara. Chloe admits to Jor-El that she is still in love with Clark.
The finale for Star Trek: The Next Generation has a Worf/Deanna Troi/Riker love triangle happen in the alternate reality. It's much of the reason why Worf and Riker were barely on speaking terms in the alternate reality.
Ziyal is in love with Garak, Garak is in something with Bashir,note Out of character, their actors have called themselves Star Trek's first gay couple, and Andrew Robinson said he played Garak as pansexual in his first appearance but the studio made him tone it down after. and Bashir has his own, uh, highly populated love life to contend with. Ziyal kisses Garak late in season 5 but then gets killed, while Bashir ends the series in a relationship with Ezri Dax.
Stargate SG-1: Samantha Carter has Unresolved Sexual Tension with Jack O'Neill throughout the series (or at least until he's Put on a Bus in season 9). They both have a succession of short-lived flirtations with aliens, most notably Sam with Martouf after she hosted the symbiote of his deceased long-term partner Rosha and inherited some of Rosha's memories, then in season 7 she starts a relationship with police detective Pete Shanahan, gets engaged, then breaks up with him (implied to be because she realized at her dying father's prompting that she's still in love with Jack).
St. Elsewhere: In "Family Feud", there are several related, increasingly complicated examples. Clancy Williams is Dr. Morrison's ex-girlfriend. Fiscus was briefly engaged to a surgical nurse named Mona Polito. The engagement was called off but Fiscus still has feelings for Mona and wants to give it another go. Clancy wants to pursue a relationship with him as she had fun when the two of them went for pizza with Pete in the previous episode "Family Ties". In the meantime, Morrison wants to get back together with Clancy but Mona invites him on a date. Things come to a head at Morrison's birthday party when everyone changes their mind so that Mona wants to be with Fiscus, who wants to be Clancy, who wants to be with Morrison, who wants to be with Mona. For his part, Ehrlich wants Mona to be with Clancy. In the next episode "Family Affair", Fiscus and Clancy go out on a date. In bed that night, Clancy admits that she was serious about dating Morrison again but realised that things would never work out between them as she thought of him more as a brother.
Stingray (1964): Atlanta Shore is in love with Troy Tempest, but in the pilot episode Troy meets and goes all dewey-eyed over Cute Mute Marina. This is such a key part of the show that it's even lampshaded in the closing titles.
The Steve, Jonathan, and Nancy triangle from Season 1 continues with Nancy and Jonathan getting together while Steve accepts it.
Joyce is dating Bob but still having tension with Hopper. It ends with Bob dying to protect Joyce, Hopper, Mike, and Will. Joyce is mourning Bob as Hopper helps her grieve.
When Max moves in, both Dustin and Lucas get crushes on her. Max chooses Lucas, and Dustin accepts.
Supergirl (2015) has established one between Kara/Supergirl, Jimmy Olsen and Winn. In an unusual case, all three remain close friends despite all being aware of the situation, though the series has so far shown Kara to be more interested, romantically, in Olsen. Olsen - who is also involved with Lucy Lane - and Winn have even been shown commiserating over the situation a few times, but so far the triangle hasn't impacted their ability to work as a team.
Sam starts dating Amelia, Amelia's father doesn't approve of their relationship because the two are each still grieving after losing someone and he thinks they're moving too fast. He can also tell Sam is hiding something. Then Amelia finds out her husband is still alive.
Invoked in "Sex and Violence", where the Siren (C) zeroes in on someone (A) who's already in a relationship (B) and uses its psychoactive saliva to force (A) to reciprocate its interest, ultimately convincing (A) to Murder the Hypotenuse. The (B) role needn't be romantic: it once targets someone who's dominated by His Beloved Smother, and later seduces Dean by promising to be a better partner to him than his brother Sam.
Simon's attraction to Jenny despite being in a relationship with Maggie in Teachers (2001)
Eric in That '70s Show was in this situation for an episode. He was dating Donna and loyal to his mother, Kitty. Kitty and Donna then start going out shopping and lunching, cutting down on Eric's intimacy with Donna.
Habib: So you're telling me that Kevin fancies me, I fancy you, and you fancy Kevin?
Third Watch: Bobby Caffey is in love with his colleague Kim Zambrano... who is still in love with her ex-husband Jimmy Doherty.
A bit more complicated one exists in The Thundermans episode "Why You Buggin?". Quinn, Link's friend from Metroberg, has an unrequited crush on Link who is going out with Phoebe and just sees Quinn as a friend. Max, meanwhile has a crush on Quinn, but she only has eyes for Link.
Tidelands (Netflix): Cal develops feelings for both Corey and Dylan. She also has sex with them both. Corey is murdered, Dylan's left stabbed in bad shape when he's last seen and so Cal may not end up with him either.
The three-season long back and forth between Telema, Kwame, and Soji in Tinsel. Then there was also Angela/Reginald/Amaka, then Reginald/Amaka/Sunom before Sunom killed Reginald.
And in Season 5, Telema/Soji/Bimpe.
Torchwood: While Jack is quite aware of Gwen's feelings for him and ambiguously returns them, he gently pushes her toward a normal relationship with her fiance ( and later husband) Rhys. Also, while Jack and Ianto's relationship is blatantly physical, the emotional aspects are brushed over until series 3.
The Twilight Zone (1959): In "From Agnes - With Love", there are two related examples. the Master Computer Agnes soon falls in love with James Elwood, who is interested in Millie. Although Millie is fond of him, Elwood's fumbling and Agnes' deliberately bad advice results in him ruining all of their dates. Agnes suggests that he introduce Millie to an inferior male so that he will look better by comparison. Unfortunately for Elwood, Agnes recommends the third-floor programmer Walter Holmes, a suave, handsome ladies' man with a blue sports car. He and Millie hit it off immediately, as Agnes knew would happen.
In "The Shadow Man", Danny Hayes has a crush on Lianna Ames, the most popular girl at Willow Creek Junior High School. However, she is dating Eric, a member of the swim team who frequently bullies Danny.
In "Opening Day", Sally Wilkerson, who is married to Carl, is having an affair with their golf instructor Joe Farrell. During a duck hunt, she has Joe arrange for Carl to be killed in a Hunting "Accident" so that the two of them can be together. When Joe does so, he finds that he and Carl have swapped places. He is now Sally's husband while Carl is her lover, whom he thinks is trying to kill him.
In "Her Pilgrim Soul", Dr. Kevin Drayton, whose marriage to Carol is failing, falls in love with Nola Granville, whose soul occupies the holographic projector that he created. It turns out that Kevin is the Reincarnation of Nola's husband Robert Goldstone and that Nola appeared to Kevin in order to provide closure for the grief that Robert suffered when she died in childbirth.
In "The Convict's Piano", Mickey Shaughnessy and Eddie O'Hara were both in love with Ellen in 1928. In order to remove his romantic rival, Mickey had Eddie framed for murder and he received a life sentence.
Utopia Falls: Aliyah is initially dating Tempo when the series starts, but then grows closer to Bodhi and kisses him.
Stefan and Damon compete for Elena (because she looks like Katherine, a woman whom they both used to be in love with).
There are lots of other triangles in the show as well, but most importantly as of the second season both of Elena's best friends also have love triangles of their own.
In The Walking Dead (2010), there is a relationship between Shane Walsh/Lori Grimes/Rick Grimes — now that Lori's husband whom Shane and Lori thought was dead has returned and the affair with Shane ended.
The Wheel of Time (2021): Rand-Egwene-Perrin, which wasn't in the books. The former two don't seem to notice, the latter denies everything, but it's an Open Secret for the rest of their friends and neighbours. Machin Shin (evil "black wind") does know and reminds Perrin of it to drive him insane. This does unhinge him a bit, which provokes Nynaeve to blurt out the secret.
World on Fire: Between Harry, Lois, and Kasia. Harry married Kasia, who goes to England with her little brother later. Harry, however, gets Lois pregnant due to a tryst they have. Kasia is extremely understanding of this, and even helps care for his baby with Lois. Neither is too keen on Harry after learning about each other, as you'd expect, and he's soon off to war anyway.
You Me Her: In Season 3, Nina becomes attracted to her boss Shaun, the bartender, and then her ex-boyfriend Andy comes back, whom she also still has feelings for. She chooses neither at first, as Nina decides working on herself is necessary at the time instead of being what men want. Then she ends up dating Shaun.
In the Dutch series Zenith, Fay is in love with Ricardo, but despite her best efforts, he has eyes only for her best friend Soraya. Unfortunately, Soraya turns out to be in love with Fay.
