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."
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: 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 Moral Event Horizon 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", didn't particularly care if their new "partner" was willing, and 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 Soap Opera 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, a solid marriage makes a boring story (though 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 Yoyo Plot Point.
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.
A few rules usually hold true in fiction: If a woman cheats, her paramour just scored a massive victory over her cuckolded husband, who is now permanently dishonored. The (male) big boss of any given workplace is likely to be two-timing his wife. The Protagonist remains sympathetic if they cheat, and becomes an innocent, wronged victim if they are the one being cheated on. Bisexuals are portrayed as incapable of faithfulness or have merely informed sexuality, and men are more prone to having affairs than women (and often portrayed as The Unfair Sex too when it comes to cheating).
- Accidental Adultery: A character cheated because he was drunk or caught in a Moment of Weakness.
- Affair Hair: The discovery of a strand of unfamiliar hair leads to accusations of infidelity.
- Affair Letters: Love letters that document someone had an extramarital affair.
- Bedroom Adultery Scene: An adulterous couple gets caught in the middle of sex by one of their spouses/partners.
- Cheating with the Milkman: A housewife has an affair with service personnel that visit the house.
- Chocolate Baby: When a newborn infant looks nothing like their "dad", implications that their mom slept with another man soon follow.
- Cuckold: The victim of infidelity, who suffers the misfortune of their spouse being unfaithful to them.
- Good Adultery, Bad Adultery: In a work with multiple instances of adultery, the adulterer is portrayed sympathetically in one instance and evil in another.
- Lipstick Mark: Lipstick on your collarbone or cheek reveals an affair.
- Mistaken for Cheating: Someone mistakenly believes their partner is cheating on them.
- The Mistress: A relatively long-term lover who is not married to her partner, especially when her partner is already married.
- Remarried to the Mistress: A man marries the same woman whom he cheated on his ex-wife with.
- Plot-Inciting Infidelity: When the plot of a story is kickstarted by having the protagonist catch their partner cheating on them.
- Really Gets Around: If someone who's already married has sex with multiple other people.
- Wedding Ring Removal: Someone removes their wedding ring before cheating on their spouse.
Unfortunately, adultery is Truth in Television, as many broken hearts and broken families will testify. It is also one of the most common reasons that people murder each other.
- Anime and Manga
- Fan Works
- Films — Live-Action
- Live-Action TV
- Video Games
- Web Comics
- Western Animation
- 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.
- Cyclops: First he kisses Jean Grey 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 Mental Affair. 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 Batman: No Man's Land, Nightwing is shown to have resumed a relationship with Oracle, but leaves a celebration early to share a New Year's kiss with Huntress.
- In Seconds, in the timeline where Katie and Max are married, Katie is still having flings with Andrew, though she does not realize this until it is pointed out to her that she is, in fact, married.
- Supergirl: In 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.
- Depending on the Writer, the Betty and Veronica dilemma in Archie Comics 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.
- Button Man: Harry has an affair with a dentist's wife for about a year. Comes into play later when Harry realizes that the man has been working with the Voices to get revenge on Harry.
- Absolutely rampant in The Wicked + The Divine, 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.
- 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.
- Black Science 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 retconned the original Golden Age Black Canary, Dinah Drake, as having cheated on Larry with her teammate Wildcat. However, most writers ignored that.
- In Robin Tim's girlfriend Ariana cheated on him a number of times, and at the end of their failed relationship Tim once kissed Stephanie in a moment of joy after she rescued him. Tim and Ari officially broke up the next day and Tim and Steph were dating by the end of the week.
- Played for Laughs in Superman (Rebirth). Superman and Superboy go to take Boyzarro (Superboy's Bizzaro duplicate) back to his universe and end up encountering Bizzaro Lois. Since normal Lois is fiercely loyal to Clark, it stands to reason that Bizzaro Lois is this trope, especially since she tries to get hot and heavy with Supes, causing him to yelp out "MA'AM!" in panic.
- 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 exactly what he asked.
- Pick a Greek myth. Any Greek myth. From Zeus (married to 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 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 Konohanasakuya-hime was accused of cheating on her husband 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).
- King Arthur: Lancelot and Guinevere, the affair of which is often cited as the cause of the fall of Camelot.
- The Bible
- 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 serious sin, forbidden by the seventh commandment. 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 Second Love 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 ....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 Didn't Think This Through.
- Later in Psalm, David begged God for forgiveness and cleanse his sin, right before delivering his own Prayer of Malice.
- Jesus commanded a woman caught in the act of adultery 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 committed adultery in his mind.
- There's a notorious edition of the Bible published in London in 1631 that became known as the "Wicked Bible" because a printing error left out a "not" to create the proscription "Thou shalt commit adultery". When this was noticed by clerical authorities a year later, the publisher was heavily fined and most copies were destroyed.
- Subverted in ECW when Beulah was found to be having an affair on Tommy Dreamer 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.
- Chyna broke with Eddie Guerrero after she found him in the shower with one of the Godfather's hoes. Their tag team partnership crumbled soon after their relationship.
- WWE Raw had an angle where Lita cheated on Matt Hardy in order to protect him from Kane. Hardy wasn't grateful and wrestled Kane for the right to marry Lita. Hardy lost but Lita then cheated on Kane with Edge. After Lita retired, Edge then began having an affair with Vickie Guerrero, with The Big Show 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 Alicia Fox.
- Buff E of the Christopher Street Connection named long time rival Matt Striker as his best man for his marriage to Tag Team 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.
- Subverted while the Age Of The Fall was running in Ring of Honor. Jimmy Jacobs wasn't happy about Lacey cheating on him with Austin Aries 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 TNA's Christian Coalition-Angle Alliance feud, Kurt's wife Karen seduced AJ Styles 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 Samoa Joe. However, when Karen started cheating on Kurt with Jeff Jarrett, Kurt was less than pleased.
- Used as a throwaway gag in The Great Muppet Caper.
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 Meet the Feebles features Bletch cheating on his girlfriend, Heidi the Hippo, with Samantha. Apparently, this is because Heidi has grown so fat and repulsive as a result of her eating disorder (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. In the climax, Heidi kills Samantha, and later kills Bletch after the latter orders his lackey, Trevor, to kill her.
- Our Miss Brooks: 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 Street Scene, Mrs. Maurrant is Cheating with the Milkman, 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 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 Cell Block Tango, which contains a minimum of four affairs, depending on how you count it.
- In 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 Divorce in Reno.
- 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 murdered or cursed him, and the gods turned her into a bridge-haunting youkai as punishment.
- In A Shot In The Dark, 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 Harold Pinter's Betrayal.
- In That Championship Season, 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 La Belle Helene is a comedic retelling of the first stages of The Trojan War, 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.
- In Hamilton, the titular character cheats on his wife... with the wife of another man, who promptly tries to blackmail him. To save face and deny allegations of embezzlement and illegal speculation with said other man, Hamilton publishes a pamphlet that boils down to "No, I did not pay this guy from the state treasury, I did it of my own pocket. What I was doing is cheat on my wife." This wrecks his career, strains his relationship with his wife Eliza, and leads to his son Phillip defending his honor in a duel.
- 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 Katawa Shoujo, the player can have a sex scene with Misha, but not only is Hisao already going out with her best friend Shizune (the person Misha is actually in love with) by this point, this whole thing leads to a bad end: Shizune never finds out about the cheating episode... but breaks up with Hisao because she blames herself for pushing Misha and Hisao away.
- In Our Personal Space, if your relationship with your husband is low enough, you can have a passionate love affair with your job assistant.
- Voltage Inc's In Your Arms Tonight is pretty much Your Cheating Heart: The Visual Novel. 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 to his boss, and that 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.
- True Love Junai Monogatari:
- The player can technically sorta do this a la Persona 4: the Player Character can romance (and bed!) almost all the prospect bachelorettes in the game if the player plays their cards right. And then it's subverted - the PC can flirt/sleep with all the girls, but only ask one of them out.
- If the Player Character is seeing 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, 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 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 Love Confession, but the deal with Remi convinced her that he was stringing her along all the time.
- Shall We Date?: Can't Say No 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, 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, they continue their affair.
- In 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 Office Lady; 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, things take an unexpected turn...
- To quote the "Hall Monitor Helen" sketch from Brandon Rogers:
"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 CollegeHumor in "Breaking Dawn Cheating Outtakes", which satirizes the publicized affair Kristen Stewart had with one of her directors, and Robert Pattinson's expected reaction to this.
- Where the Bears Are: Wood, Wood, Wood. He has a sexual relationship with 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 Vox and King Beau, Beau helps Vox discover that her boyfriend is cheating on her.
- The Jenkinsverse: Ava Rios, who cheats on her high-school beau Adam after years of long-distance relationship.
- In SuperMarioLogan's "Toad's Girlfriend!", this is all over the place and all Played for Laughs.
- In Twelve Hundred Ghosts, despite Bob Cratchit being married, he thinks Scrooge yelling at him is the hottest thing he'd ever seen.