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-> ''"Your cheatin' heart will make you weep,\\
You'll cry and cry and try to sleep.\\
But sleep won't come the whole night through,\\
Your cheatin' heart will tell on you."''
-->-- '''Music/HankWilliams''', "[[TropeNamers Your Cheatin' Heart]]"

Two-timing, playing away from home, having a bit on the side, going behind your partner's back, adultery, infidelity... There are a lot of names for cheating on your partner, but most of them have the same outcome: [[LoveHurts a world of hurt.]]

Most of us recognize this type of plot: Bob is married to Alice. One day, Bob sees Carol at a club and is attracted to her. Perhaps things haven't been going so well with Alice for some time. Maybe they just had a major fight and Bob stormed off. Or maybe his marriage is perfectly healthy, and Bob has no excuse. Whatever the reason, Bob flirts with Carol, which eventually leads to a sexual or romantic relationship and the various things that entails. But here's the thing: Bob doesn't tell Alice about it. He doesn't dump her, he doesn't tell her that he thinks the marriage is on the rocks, he doesn't talk to her about {{Polyamory}} or swinging, he doesn't even ask for "more space". He continues to play the part of her husband, and expects her to continue being his wife, hoping that Alice won't notice when he starts coming in late for dinner, or ask him about the mysterious expenditures on their joint account. Sometimes, just to really play Alice for a sucker, their marriage will seemingly ''improve''-- he buys Alice gifts, pays attention to her and seems much happier, but all the while he's running off to see Carol. For extra scumbag points, he may be keeping Carol similarly in the dark about Alice. Chances are he'll eventually get caught; if he didn't, the story wouldn't have the same dramatic impact. A lot of angst and tension will ensue.

Way back in the day, when marriage was considered permanent and divorce was a word whispered fearfully by gossiping old ladies, The Affair was a shocker of a storyline, and very often an automatic MoralEventHorizon for the cheating partner. However, it's worth noting that even further back in the day, the gods, goddesses and minor side characters of mythology listed "infidelity" under "Hobbies", [[DoubleStandardRapeDivineOnMortal didn't particularly care if their new "partner" was willing]], and [[KarmaHoudini got away with it]]. Only their mortal lovers got the nasty side of the wronged wife's/husband's temper when the affair was discovered.

Nowadays, affairs are common in any SoapOpera and turn up an awful lot in other types of story as well. We don't really ''expect'' a fictional husband and wife to stay faithful to each other for forty or so years. Supposedly, [[TrueLoveIsBoring a solid marriage makes a boring story]] (though [[HappilyMarried some would disagree]]). Often, a sequence of "get together → one cheats → they break up → they make up → the other one cheats", and so on) will be followed so often and so tiresomely that it becomes a YoyoPlotPoint.

What ''defines'' cheating usually depends on the context of the story and the characters involved. Stories aimed at younger audiences, or with a clear emphasis on romantic, monogamous relationships, will probably count kissing and flirting as cheating. Most examples of cheating in shows aimed at adults, however, will involve sex. Occasionally, characters may clash specifically because they have different definitions of cheating: for example, the husband who protests that he was drunk and it was "just a kiss" to his furious wife, or a girlfriend who can't understand why her boyfriend doesn't like her flirting with her male friends.

[[GoodAdulteryBadAdultery A few rules]] usually hold true in fiction: If a woman cheats, her paramour just scored a ''massive'' victory over her {{cuckold}}ed husband, who is now permanently dishonored. The (male) big boss of any given workplace is likely to be two-timing his wife. TheProtagonist [[ProtagonistCenteredMorality remains sympathetic if they cheat]], and becomes an innocent, wronged victim if they are the [[GoodAdulteryBadAdultery one being cheated on]]. [[DepravedBisexual Bisexuals are portrayed as incapable of faithfulness]] or have [[UrbanLegendLoveLife merely informed sexuality]], and men are more prone to having affairs than women (and often portrayed as TheUnfairSex too when it comes to cheating).

* AccidentalAdultery: A character cheated because he was [[ButLiquorIsQuicker drunk]] or caught in a {{Moment of Weakness}}.
* AffairHair: The discovery of a strand of unfamiliar hair leads to accusations of infidelity
* AffairLetters: Love letters that document someone had an affair
* BedroomAdulteryScene
* CheatingWithTheMilkman: A housewife has an affair with service personnel that visit the house
* {{Cuckold}}: Victim of infidelity
* GoodAdulteryBadAdultery: In a work with multiple instances of adultery, the adulterer is portrayed sympathetically in one instance and evil in another.
* LipstickMark: Lipstick on your collarbone or cheek reveals an affair
* MistakenForCheating: Someone mistakenly believes their partner is cheating on them
* TheMistress: A relatively long-term lover who is not married to her partner, especially when her partner already married
* PlotIncitingInfidelity: When the plot of a story is kick started by having the protagonist catch their partner cheating on them.
* SympatheticAdulterer: Cheater portrayed sympathetically
* TheUnfairSex: Women who cheat are often portrayed more sympathetically than men.
* WeddingRingRemoval: Someone removes their wedding ring before cheating on their spouse

Unfortunately, adultery is TruthInTelevision, as many broken hearts and broken families will testify. It is also one of the most common reasons that people murder each other.

See GoodAdulteryBadAdultery. This is generally the #7 scenario of TriangRelations.

* YourCheatingHeart/AnimeAndManga
* YourCheatingHeart/FanWorks
* [[YourCheatingHeart/LiveActionFilms Films Live-Action]]
* YourCheatingHeart/{{Literature}}
* YourCheatingHeart/LiveActionTV
* YourCheatingHeart/{{Music}}
* YourCheatingHeart/VideoGames
* YourCheatingHeart/WebComics
* YourCheatingHeart/WesternAnimation


[[folder:Comic Books]]
* Comicbook/{{Gambit}} who been hitting on Rogue for half-a-dozen issues before his estranged wife Belladonna suddenly turned up. More sympathetic than most examples of this trope.
* ComicBook/{{Cyclops}}: First he kisses ComicBook/JeanGrey when she is resurrected although he was married to Maddeline Prior (at the time, it should be noted, Maddie had let him think that she was dead), and then much later he cheats on Jean Grey (now his wife) with Emma Frost in a MentalAffair. In the latter case, Frost was his therapist at the time and took advantage of his crippling vulnerability in a spectacular violation of medical ethics.
* In ''ComicBook/BatmanNoMansLand'', Nightwing is shown to have resumed a relationship with Batgirl, but leaves a celebration early to share a New Year's kiss with Huntress.
* In ''ComicBook/{{Seconds}}'', in the timeline where [[spoiler:Katie and Max are married]], Katie is still having flings with Andrew, though she does not realize this until [[spoiler:it is pointed out to her that she is, in fact, married]].
* ComicBook/{{Supergirl}}: In ''[[ComicBook/Supergirl1972 Supergirl Vol. 1]]'' #9, the titular heroine finds out that her then-boyfriend Dale was cheating on her. When she chews him out before breaking up, he is completely unapologetic about his actions.
* DependingOnTheWriter, the BettyAndVeronica dilemma in ''ComicBook/ArchieComics'' is this, though usually it's written as neither girl being Archie's steady girlfriend. If not that, then Archie usually breaks up with one of them before dating the other.
* ''ComicBook/ButtonMan'': Harry has an affair with a dentist's wife for about a year. Comes into play later when [[spoiler:Harry realizes that the man has been working with the Voices to get revenge on Harry.]]
* Absolutely ''rampant'' in ''Comicbook/TheWickedAndTheDivine'', though justified as it's about a bunch of mostly sex and war gods as out-of-control young people looking death in the face on the cusp of adulthood.
* ''[[ComicBook/SilentHill Silent Hill: Sinner's Reward]]'': Jill, wife of the mob boss who hired Jack, became attracted to Jack upon meeting him (and the feeling is mutual). She and Jack leaving together, and the mob boss' decision to have them brought back to him, triggered the plot.
* ''ComicBook/BlackScience'' features Grant's long-running affair with his lab coworker Rebecca. When Pia realizes it, she implies it's not the first time he's strayed.
* One writer {{retcon}}ned the original Golden Age Black Canary, Dinah Drake, as having cheated on Larry with her teammate Wildcat. However, most writers ignored that.

[[folder:Film -- Animation]]
* {{Subverted|Trope}} regarding Xibalba from ''WesternAnimation/TheBookOfLife''. WordOfGod stated that it only looked like he cheated on La Muerte with other goddesses, but he never actually did.
* In ''WesternAnimation/StrangeMagic,'' Marianne catches her fiancé [[JerkAss Roland]] cheating on her [[EstablishingCharacterMoment right before]] her wedding.

* A man bets his wife that she can't say something that will make him happy and sad at the same time. She tells him that out of him and his friends, he has the biggest penis.
* A man sees an ad offering a gently-used Porsche for the comically-low price of $20. Intrigued, he shows up. The Porsche is there, it's real. He takes it on a test drive, it runs just fine. So he asks the woman selling it why she's willing to let it go for so cheap. She explains that the Porsche technically belongs to her husband, who recently ran away with his secretary. So when he calls back home and says "sell the Porsche and send me the money", she's doing ''{{exact|Words}}ly'' what he asked.

[[folder:Myths & Religion]]
* Pick a Greek myth. Any Greek myth. From Zeus (married to [[BrotherSisterIncest his sister, Hera]]) seducing or outright raping everyone, male or female, to Aphrodite (married to long-suffering Hephaestus) and her relationship with Ares, to Paris eloping with Helen of Troy, the wife of Menelaus... no wonder there were so many children [[HeroicBastard of questionable parentage]] running around.
* Over in Norse mythology, we have Sif - married to Thor, and though it was never confirmed to be true or false, Loki at one point accused her of sleeping with him ("Only I know, as I think I do know/Your love besides Thor/And that was the wicked Loki!"). She says nothing, and then another goddess starts talking. And in an earlier myth, Odin (in disguise) said to Thor the equivalent of "Hey, no need to hurry home to your wife or anything, because she's got someone else to keep her bed warm!" Both times, Thor was understandably pissed.
* In Japanese myths, the flower goddess and Mount Fuji patron [[http://en.wikipedia.org/wiki/Konohanasakuya Konohanasakuya-hime]] was accused of cheating on her husband [[http://en.wikipedia.org/wiki/Ninigi Ninigi-no-mikoto]], the grandson of Amaterasu, since she announced her pregnancy ''the day after their marriage.'' Her reply was to lock herself in a burning hut to give birth, saying that her baby wouldn't be hurt if they truly were the offspring of Ninigi. She was proved right... and gave birth to healthy triplets (Hoderi, Hosuseri, and Hoori).
* Myth/KingArthur: Lancelot and Guinevere, the affair of which is often cited as the cause of the fall of Camelot.
* ''Literature/TheBible''
** God's people Israel is portrayed in the book of Ezekiel as an unwanted baby girl whom God raised up to be a lovely woman, whom He married and took good care of and made her even more beautiful, who ended up becoming unfaithful to her husband by having sex with other people, as a picture of how God's people had become unfaithful to Him and had given themselves over to idolatry.
** Adultery in general is considered as a sin. The Book of Corinthian provides a detailed definition about this subject: In order to prevent sexual immorality, Paul insisted that marriage and a long-lasting relationship is a preferable solution. If the spouse is a non-believer and still follows a believer, the believer is not allowed to propose a divorce. The only two occasions where one can legitimately seek a SecondLove is if the spouse was deceased (which ends the bond of marriage), or if a non-believer left the believer.
** David commits adultery with Bathsheba and after several failed attempts to get her husband Uriah to go home and sleep with her (in order to make it seem that Uriah had conceived the child that resulted from their tryst), David decides to indirectly murder him using a [[UriahGambit ....what else?]]. It works. Although considering the impossibility of hiding anything from God and the punishment that resulted from this sin, nobody would be blamed for saying that David DidntThinkThisThrough.
*** Later in ''Psalm'', David begged God for forgiveness and cleanse his sin, right before delivering his own PrayerOfMalice.
** Jesus commanded a woman caught in the act of adultery [[GoAndSinNoMore not to sin anymore]] after the men who wanted to condemn and stone her to death left the scene upon being reminded that they also had sinned. He himself also said whoever lusted after a woman upon seeing her has [[{{Thoughtcrime}} committed adultery in his mind]].

[[folder:Pro Wrestling]]
* {{Subverted|trope}} in Wrestling/{{ECW}} when Wrestling/{{Beulah|McGillicutty}} was found to be having an affair on Wrestling/TommyDreamer with another woman. After some apprehension, Dreamer declared he would take them both, because he's hardcore, though in the end he ended up with just Beulah.
* Wrestling/{{Chyna}} broke with Wrestling/EddieGuerrero after she found him in the shower with one of the Godfather's hoes. Their tag team partnership crumbled soon after their relationship.
* Wrestling/WWERaw had an angle where Wrestling/{{Lita}} cheated on Wrestling/MattHardy in order to [[ScarpiaUltimatum protect him]] from Wrestling/{{Kane}}. Hardy wasn't grateful and wrestled Kane for the right to marry Lita. Hardy lost but Lita then cheated on Kane with Wrestling/{{Edge}}. After Lita retired, Edge then began having an affair with Wrestling/VickieGuerrero, with Wrestling/TheBigShow trying to get Guerrero to leave Edge for himself but what brought it an end was Edge attempting to cheat on ''her'' with their wedding planner Wrestling/AliciaFox.
* Buff E of the Christopher Street Connection named long time rival Matt Striker as his best man for his marriage to TagTeam partner Mace Mendoza but during the ceremony Striker had enough and announced that Buff E and himself had been having an affair. This lead Mendoza to admit he had also been cheating on Buff E with his maid of honor Dana Dameson and gotten her pregnant. The wedding was off but they agreed to keep working as a tag team.
* Wrestling/{{Subverted|trope}} while the Age Of The Fall was running in Wrestling/RingOfHonor. Wrestling/JimmyJacobs wasn't ''happy'' about Lacey cheating on him with Wrestling/AustinAries but was willing to take her back, to prove he wasn't jealous and that love was more important than sex. Lacey, however, couldn't bring herself to do it.
* During Wrestling/{{TNA}}'s Wrestling/{{Christian}} Coalition-Angle Alliance feud, Kurt's wife Karen seduced Wrestling/AJStyles to bring the former group under the control of the latter and Kurt for his part ''didn't care'', at one point giving Karen to AJ so she wouldn't distract him from more important things like beating Wrestling/SamoaJoe. However, when Karen started cheating on Kurt with ''Wrestling/JeffJarrett'', Kurt was less than pleased.

[[folder:Puppet Shows]]
* Used as a throwaway gag in ''Film/TheGreatMuppetCaper''.
-->'''Gonzo:''' How about you folks? Souvenir photograph?\\
'''Man:''' No thanks. No pictures.\\
'''Gonzo:''' Oh, come on! It'll be a great memento for you and your wife.\\
'''Man:''' My wife isn't feeling very well.\\
'''Gonzo:''' Oh, that's too bad. Maybe she should be at home.\\
'''Man:''' My wife IS at home!\\
'''Gonzo:''' ''[stammers incoherently]'' Yes, uh... NEXT TABLE!
* One of the sub-plots in ''Film/MeetTheFeebles'' features [[WilyWalrus Bletch]] cheating on his girlfriend, Heidi the Hippo, with [[CatsAreMean Samantha]]. Apparently, this is because Heidi has grown so fat and repulsive as a result of her eating disorder ([[{{Hypocrite}} despite Bletch being just as fat]]). Heidi eventually finds out, and is so heartbroken she refuses to perform, though Bletch manages to lift her spirits by having make-up sex with her. However, he still dumps her later. [[spoiler: In the climax, Heidi [[MurderTheHypotenuse kills Samantha]], and later [[DeathByWomanScorned kills Bletch]] after the latter orders his [[TheDragon lackey]], [[YouDirtyRat Trevor]], to kill her.]]

* ''Radio/OurMissBrooks'': In "Four Fiancés ", Miss Enright, masquerading as Miss Brooks, corresponds in her name with four different men... and proposes marriage to each and every one of them! To get rid of her Texas fiancé, Miss Brooks pretends that Mr. Conklin (who had brought over Miss Enright to force an apology from her) is her straying husband and Miss Enright the other woman!

* In ''Theatre/StreetScene'', Mrs. Maurrant is CheatingWithTheMilkman, who the neighbors point out is himself married with two children. Her daughter Rose is aggressively propositioned by her boss, Harry Easter, who tells her that his wife doesn't need to know about anything he's planning.
* In ''Theatre/{{Chicago}}'', Roxie is cheating on her husband Amos with Fred Casely, a married man whom she shoots to death at the start of the play; Amos grudgingly stands by his wife until she decides to draw sympathy in her murder trial by pretending to be pregnant. The musical also has [[http://www.stlyrics.com/lyrics/chicago/cellblocktango.htm Cell Block Tango]], which contains a minimum of four affairs, depending on how you count it.
* In ''Theatre/{{Allegro}}'', when Joe moves to the big city, it turns out that his wife is cheating on him with Lansdale, the benefactor of the hospital he works for. He finds this out from Mrs. Lansdale, who's on her way to DivorceInReno.
* In Noh theatre, the bridge princess youkai is the eternally-jealous spirit of a noblewoman whose husband cheated her. Depending on the retelling, she either [[DeathByWomanScorned murdered]] or cursed him, and the gods turned her into a bridge-haunting youkai as punishment.
* In ''Theatre/AShotInTheDark'', it gradually emerges that while the first suspect was cheating on the victim with the master of the house, his wife was having an affair with his best friend. Sevigne helps make the point that while adultery "is not illegal--it's not even unpopular," murder is "certainly illegal, and probably unpopular."
* Everyone in Creator/HaroldPinter's ''Theatre/{{Betrayal}}''.
* In ''Theatre/ThatChampionshipSeason'', Phil Romano and his wife Claire have a functionally open marriage. One of Phil's lovers is Marion Sitkowski, the wife of his friend, former high school basketball teammate, and current mayor George Sitkowski, who makes things easier for Phil's strip mining operations in exchange for generous campaign donations. When George's campaign manager, James Daley, tells George that one of his top campaign donors is also sleeping with his wife, George takes it so badly that he points a loaded rifle at Phil. Phil insists that Marion participated in the affair to further George's political career.
* Offenbach's operetta ''Theater/LaBelleHelene'' is a comedic retelling of the first stages of TheTrojanWar, in which Menelaus is just about the only one who cares that the gods have more or less sent his wife to commit adultery (the other kings are more concerned with keeping the gods on their side). One of the songs explains why a husband returning home early has only himself to blame for finding his wife in bed with another man.

[[folder:Visual Novels]]
* This is how you get bad endings for ''all four'' of the girls from ''Eroge! Sex And Games Make Sexy Games'' in their routes; by giving into temptation from other women while in a relationship with either Iori, Momoka, Kisara, or Nene.
* In ''VisualNovel/KatawaShoujo'', the player can have a sex scene with [[spoiler:[[GenkiGirl Misha]]]], but not only is Hisao already going out with [[spoiler:her best friend Shizune (the person [[SchoolgirlLesbians Misha]] is ''actually'' in love with)]] by this point, this whole thing leads to a bad end: [[spoiler:Shizune]] never finds out about the cheating episode... but breaks up with Hisao because she blames ''herself'' for pushing [[spoiler:Misha]] and Hisao away.
* In ''VisualNovel/OurPersonalSpace'', if your relationship with your husband is low enough, you can have a passionate love affair with your job assistant.
* Voltage Inc's ''VisualNovel/InYourArmsTonight'' is pretty much Your Cheating Heart: The VisualNovel. The story is kicked off by the protagonist discovering that her new husband of three months is cheating on her with another woman; although she can choose to summarily divorce him, in several of the game's possible routes she attempts to stick it out and make their marriage work only to fall in love with another man.
** In the route focusing on the protagonist's husband, Koichi, it's eventually revealed that his mistress is also married [[spoiler:to his boss]], and that [[spoiler:his father has a long-standing relationship with another woman which Koichi's mother knows about and refuses to acknowledge, a fact which goes towards explaining Koichi's skewed perspective on his own marriage]].
* ''VisualNovel/TrueLoveJunaiMonogatari'':
** The player can ''technically'' sorta do this a la ''VideoGame/{{Persona 4}}'': the PlayerCharacter can romance (and bed!) ''almost all'' the prospect bachelorettes in the game if the player plays their cards right. [[spoiler:And then it's subverted - the PC can flirt/sleep with all the girls, but ''only'' ask one of them out.]]
** If the PlayerCharacter is seeing [[LoveTriangle both Mikae and Remi]] and has ''very'' high points with both girls, he'll get the chance to date Remi on the 27th of September and Mikae on the 28th. If it happens, [[spoiler:Mikae will believe he had sex with Remi (even if he didn't), call him a bastard and leave in a huff, ruining the chances with her forever.]] Not only it's the ''only'' time the player gets directly punished for pursuing more than one girl, but [[spoiler:properly romancing Mikae will explain ''why'' does she explode like that: she had liked the guy for years already and was getting ready to give him her own LoveConfession, but the deal with Remi convinced her that he was stringing her along all the time.]]
* ''VisualNovel/ShallWeDateCantSayNo'' is pretty much built around the trope too:
** The protagonist, Kana Saeki, at least has the option to cheat on her boyfriend Kaoru (who has been neglecting her and refusing to meet up in dates) in every route, and ''will'' unavoidably cheat during Subaru or Akira's routes.
** Akira is married, and in his route Kana becomes the "other woman." In his Happy Ending, [[spoiler:he leaves his wife and proposes to Kana, who privately wonders about the likelihood that he'll cheat on her with someone else in the future even as she accepts]]. In his Normal Ending, [[spoiler:they continue their affair]].
** In [[spoiler: Subaru]]'s route, it turns out Kaoru ''is'' cheating on Kana.
* In the H-game ''Please bang my wife'', Yasushi's wife Mariko is a beautiful OfficeLady; she cheats on him with her boss because he's a ''far'' better lay. Yasushi logically gets jealous when he confronts her, but after Mariko explains herself... well, [[NetoRare things take an unexpected turn]]...

[[folder:Web Original]]
* To quote the [[https://youtu.be/0tjBBO2SUbE "Hall Monitor Helen"]] sketch from Webvideo/BrandonRogers:
-->"Three years ago, my husband went out one night for a beer, but that beer was ''all the way'' in Tennessee and had much bigger tits."
* Parodied by ''Website/CollegeHumor'' in "[[http://www.youtube.com/watch?v=GK9TLD-1W0s Breaking Dawn Cheating Outtakes]]", which satirizes the publicized affair Creator/KristenStewart had with one of her directors, and Creator/RobertPattinson's expected reaction to this.
* ''WebVideo/WhereTheBearsAre'': Wood, Wood, Wood. He has a sexual relationship with [[spoiler:Detective Winters, and then gets into one with Detective Martinez. He's not exclusive with either, but he still tries to keep each cop from finding out about the other. It turns out that the detectives are married, and in fact neither knows that the other is banging Wood.]]
* At the beginning of WebOriginal/VoxAndKingBeau, [[NotSoImaginaryFriend Beau]] helps Vox discover that her boyfriend is cheating on her.
* ''Literature/TheJenkinsverse'': [[spoiler:Ava Rios, who cheats on her high-school beau Adam after years of long-distance relationship.]]
* In ''WebVideo/SuperMarioLogan's'' "Toad's Girlfriend!", this is all over the place and all ''PlayedForLaughs''.