->''"And God spake all these words, saying...\\
Thou shalt not kill."'' [[note]]The phrase actually translates to "Thou shalt not murder." "Thou shalt not kill" is an Elizabethean translation, and there's been some semantic drift since. It would be strange for the Old Testament to forbid every manner of killing, given the times when God is said to have ordered the Israelites to kill, e.g., wiping out the Amalekites.[[/note]]
-->-- '''Literature/TheBible''', ''[[Literature/BookOfExodus Exodus]] [[TropeNamers 20:1,13]]''

Ending a life is [[BackFromTheDead usually]] a permanent thing. There's no way to say "I'm sorry", or to make up for it later. And for some people, killing is a line they ''will not cross'', no matter how much the death might serve the greater good (or, in some cases, the greater evil). "He needed killing" is not in these people's vocabulary.

This is common in works with BlackAndWhiteMorality, but even appears in works with GreyAndGrayMorality. In the latter, it's sometimes the only way to tell the "good" guys from the "bad" guys.

[[WhatMeasureIsANonHuman Opinions differ on how this applies to sentient life other than humans.]] In general, it's still up to BigDamnVillains to kill other villains. It's perfectly fine to [[ImmortalLifeIsCheap "kill" immortals though]] as it is to kill the undead. The MercyKill sometimes winds up as an exception. KarmicDeath, SelfDisposingVillain, and HoistByHisOwnPetard provide alternate ways to kill off villains without forcing the heroes to get their hands dirty.

Thou Shalt Not Kill is closely related to JokerImmunity. Whilst many writers believe a never-kill creed makes the hero more likable and righteous, on another level it might simply be a plot device [[StatusQuoIsGod to prevent the hero from killing off popular recurring villains]]: the rationale is that if a hero, say, Franchise/{{Superman}} were to kill a bad guy in one story, why wouldn't he simply resolve all of his problems by, for example, incinerating ComicBook/LexLuthor with his heat vision on sight? Related is PacifismBackfire, where their reluctance to fight (or to kill as in this trope) may cause JokerImmunity. This trope is more common in serial fiction, such as TV shows and comic books, rather than one-shots like movies. In action movies [[SuperheroMovieVillainsDie it is common and acceptable for the hero to kill the villain]] because there is usually no planned sequel for the villain to appear in. It's also somewhat common for both stand alone and serial storytelling to feature a character who begins adhering to this trope, but over the course of various dramatic devices, such as a TraumaCongaLine, is finally forced to - or chooses to - cross the line.

With superhero characters, attitudes toward no-kill policies range from utterly ignoring it (such as the protagonists of ''ComicBook/{{Watchmen}}''), to treating it as a [[BewareTheNiceOnes preferred outcome]] (such as Superman), to strict adherence to it in all cases (such as Franchise/{{Batman}}). Whatever the moral case is, this trope is often used to show off the hero's incredible precision, whether it be with a fist or a gun. This can include things like [[BlastingItOutOfTheirHands separating the mook from their weapon with a precisely aimed bullet]], or possibly [[TapOnTheHead knocking an opponent out]]. Whatever the case, their non-lethal attacks are due to their incredible skill. Note that this often a case of RealityIsUnrealistic as many of these attacks are very capable of causing serious injury or death.

"Thou shalt not kill" is derived from the Bible's Ten Commandments, and the religious implications of taking life in apparent violation of this commandment (which is often translated as "Thou shalt not murder," which results in debates over semantics) are sometimes also invoked in storytelling.

SubTrope to NoHarmRequirement where characters for one reason or another are restricted in how much harm they can deal to or allow another being to take, if any.

See also KickThemWhileTheyAreDown, ActualPacifist, RecklessPacifist, TechnicalPacifist, MartialPacifist, NonLethalWarfare, WouldNotShootAGoodGuy, and RestrainedRevenge. For a similar trope in video games, see PacifistRun.

* ThouShaltNotKill/AnimeAndManga
* ThouShaltNotKill/ComicBooks
* ThouShaltNotKill/FanWorks
* [[ThouShaltNotKill/AnimatedFilms Films Animated]]
* [[ThouShaltNotKill/LiveActionFilms Films Live-Action]]
* ThouShaltNotKill/{{Literature}}
* ThouShaltNotKill/LiveActionTV
* ThouShaltNotKill/VideoGames
* ThouShaltNotKill/WesternAnimation
* ThouShaltNotKill/RealLife


[[folder: Newspaper Comics]]
* In the storyline which introduces Bluto, ComicStrip/{{Popeye}} has to use his most powerful punch, and is extremely worried about Bluto's survival. This happened in 1932, [[OlderThanTheyThink before either Marvel or DC was even founded]].

* ''Radio/TheLoneRanger'', in some ways a precursor to Vash, used silver bullets as a symbol of his pledge never to take human life.

[[folder:Stand-Up Comedy]]
* In Creator/GeorgeCarlin's routine on The Ten Commandments, he ends with this one and says that, because more people have been killed in the name of God than for any other reason[[note]]Untrue, of course. Neither Hitler nor Stalin nor Mao invoked any God before killing millions of their own people, Jenghiz Khan didn't care two hoots about religion, and we could go on and on with this.[[/note]], it really comes down to who's doing the killing and who's getting killed. He decides it should be renamed "Thou shalt try ''really'' hard not to kill anyone, unless they prey to a different invisible man from the one you prey to."

[[folder: Tabletop Games]]
* ''TabletopGame/{{GURPS}}'' has the Pacifist disadvantage, which comes in several flavors, one of which is Cannot Kill. Characters with the "Cannot Kill" disadvantage can start fights and use any tactics they like, but they cannot kill, or be responsible for a death, or leave a wounded enemy to die. They also cannot stand by while their teammates administer the CoupDeGrace. If they do, they {{angst}} about it for days and are effectively rendered useless to the team.
* Some Superhero {{RPG}}s would invoke rules against killing. Two notable examples were ''TabletopGame/MarvelSuperHeroes'' and ''TabletopGame/DCHeroes'', which would eliminate all Karma/Hero Points (a combination of experience points, and self-boosting reserves for various tasks) and keep you from accumulating more for the rest of the adventure (usually one night of gaming). In DC heroes, this punishment came from using lethal force at all.
* ''TabletopGame/DungeonsAndDragons'' has the Book of Exalted Deeds, which contains the feat "Vow of Peace". It grants benefits as long as you don't inflict lethal damage, allow an ally to finish off a defeated opponent, or cause similar harm to a creature. It takes this trope to extremes; accidentally swallowing a gnat in your drinking water will cause you to lose the benefits of the feat, in fact the feat specifically references paladins drinking their water through a strainer. It doesn't really make you a pacifist, [[TechnicalPacifist technical]] or [[ActualPacifist actual]], though; you can still fight all you want, as long as you never inflict lethal damage.
* "Code vs. Killing" is one of the most commonly seen Psychological Limitations in ''TabletopGame/{{Champions}}'', usually bought as "total commitment" (i.e. the character can't bring him- or herself to kill at all and won't stand idly by while others do it either). Normal people are already assumed to be "reluctant to kill" by default (being AxCrazy would be its own different Limitation); the code, if taken, is intended to go beyond well beyond that to proper comic book levels. Of course, being a Limitation that you get points for, it's also ''supposed'' to cause your character trouble from time to time.
* In the TabletopGame/OldWorldOfDarkness, Lifesaver is a 3 point flaw that makes you unwilling to take life. Pacifist is a 5 point flaw and is taken literally - the character can do no physical harm to others.

[[folder: Web Comics]]
* In ''Webcomic/SluggyFreelance'', Torg made Oasis swear one of these vows. She sorta forgets it for a while and becomes an AllCrimesAreEqual vigilante. When she remembers, she cries, "I've broken my promise! There can be no wedding! ''Why does love bring me nothing but pain?''" Ironically, Torg himself doesn't really subscribe to this philosophy, as he was perfectly willing to go in guns blazing and swords swinging during "The Stormbreaker Saga" and "Dangerous Days" arcs.
* In ''WebComic/TheAdventuresOfDrMcNinja'' [[spoiler: Mongo the superninja has learned the preciousness of life.]] [[Film/{{Frankenstein|1931}} And also]] that [[AltText fire bad]].
* ''Webcomic/DemonFist''
** The Demon Fist almost never kills humans or peaceful demons, even (especially!) {{Mooks}}.
** Neither does the Hookshot crew. This pays off for them later.
-->'''Duncan:''' Your crew fought off all my men without killing any of them. Criminals would not have wasted the effort not to kill their attackers. I can't in good conscience take you all in simply for defending yourselves.
* Decoy Octopus of ''WebComic/TheLastDaysOfFoxHound'' passes The Sorrow's test because he has never killed anyone and thus has no one to face. The Sorrow is ''very'' surprised and Octopus just shrugs, claiming he's more suited for espionage than fighting.
* ''Webcomic/SchlockMercenary'': Petey avoids killing if at all possible, and at one point refuses to let a spy go back home because she'll just get needlessly mind-ripped. After [[spoiler:the oafans give everyone immortality]], he starts going to truly absurd lengths to avoid killing, like teraporting entire fleets that are in the middle of a massive fight. As he says, he can't be sure these people will still be his enemies in hundreds or thousands of years, so killing ''anyone'' is like killing future allies.


[[folder: Web Original]]
* This trope was actively enforced in the ''Roleplay/GlobalGuardiansPBEMUniverse''. Player characters who were [[AxeCrazy casual killers]] were absolutely not welcome, and those that became it later were booted from the game. Accidents still happened, but for the most part the idea the various campaigns operated under was that real heroes didn't kill criminals. The single exception was the ''Big Easy'' campaign, but as that campaign was based on UsefulNotes/TheDarkAgeOfComicBooks, it got a pass.
* Shortly after 9/11, WebSite/TheOnion reported that {{God}} [[http://www.theonion.com/articles/god-angrily-clarifies-dont-kill-rule,222/ held a press conference]] to remind everyone exactly what He meant by "Thou Shalt Not Kill."
* Averted with extreme prejudice in the Literature/WhateleyUniverse. It's a sad commentary on a superheroic [[TheVerse 'verse]] when the person best known for having a code against killing is a super''villain'' (Mimeo, a veru high-end [[PowerCopying Power Mimic]], so it is not just out of good intentions - he wants to be able to keep getting the power-up from fighting superheroes so he can go after his real targets, meaning that killing his 'donors' would be counterproductive).
** All but two of the members of Team Kimba (who are high school students) have been responsible for multiple deaths, and Jade in particular has a body count around 100 - most of them over ''Christmas vacation'' in their freshman year.
** It has been mentioned that in addition to several deadly encounters with [[spoiler:Nazi spies during WWII]], a number of villains have died fighting [[BigGood Lady Astarte]] due to accidents; like most superheroes, she doesn't choose to kill ([[spoiler:and it is a major CharacterDevelopment moment that she would actually try to kill Deathlist during his attack on the school]]), but supervillainy is a dangerous field at the best of times, and even in cases where she could do something, she sees herself as being under no obligation to save them from their own mistakes if it would put others at risk.
** In addition, many supposed superheroes and costumed vigilantes show little compunction about killing. The Dark Avenger and the Lamplighter are two of the better known examples, but far from the only ones. This isn't even considering 'heroes' like Jack Rabbit or Iron Mike, who are basically thugs and thieves pretending to be heroes.
* ''Literature/HeroesSaveTheWorld'': Austin Smith is trying to adhere to this as much as he can. It's disquieting for him when he learns that he has the greatest potential for mass destruction out of the Children located thus far.
* The Red Panda and Flying Squirrel of ''Podcast/RedPandaAdventures'' go out of their way to avoid using lethal force. Though the Red Panda owns a katana, for example, he won't take it into battle so as to not even have the option. They fight with fists, gadgets, and hypnosis. They aren't as firmly wedded to it as other superheroes with a "no killing" code, however. They can and will employ lethal force if the situation calls for it. Fighting non-living foes such as Professor Zombie's undead minions naturally falls into this, but the pair have also been willing to kill if the entire city, or even world is at stake, such as killing the Nazi Ubermensch, Tevas, to keep him away from the Normandy invasion. The one thing that will make either the Red Panda and Flying Squirrel outright ''abandon'' this edict is if a villain seems to have killed one or the other. A developing VillainTeamUp decides against killing the Squirrel to get to the Red Panda precisely because they know it ''will''.