A very common weakness shared among The Undead is fire. Chopping such creatures into little bits may not stop them, but fire generally will. They also often burn more readily than is strictly realistic.
The undead's weakness to fire is often connected with the idea that Fire Purifies: life-giving fire—the opposite of the dead, cold, unholy undead—is particularly effective at sending such critters back to their graves for good. In the case of vampires, a weakness to fire may be connected to, or contain, a weakness to sunlight.
Sometimes the internal justification for this trope is that the undead regenerate (part of the same magic that keeps dead flesh and bones moving at all), and all monsters who regenerate in the setting are vulnerable to fire, likely due to the fact that fire destroys with a completeness that little else can match. Or, for ghostly undead, fire and other energy attacks may be less likely to pass through them than physical ones. In the case of zombies, it's often tied into some variation of killing The Virus (similar to the practice of cremating the bodies of those who died from illness to prevent the spread of infection), destroying the brains by frying them, or, failing that, destroying and melting enough muscle and cartilage to prevent them from moving.
Vampires are particularly associated with this trope, but it is certainly not limited to them.
A subtrope of Fire Purifies and Weak to Fire. Frequently overlaps Fire Keeps It Dead, which is where burning prevents creatures from coming back to life in the first place (the overlap is when killing undead with fire also stops them from respawning). Also compare Burn the Witch!, which has similar reasoning behind it. Contrast Infernal Retaliation, where trying to set an undead on fire simply makes things worse for you. This is a common property of Sacred Flames.
- In Inuyasha the Movie: Swords of an Honorable Ruler, the evil sword So'unga reanimates anyone slain by it as zombies that can only be slain again by burning their bodies. This makes Jaken and Totosai, who are normally just comic relief, actually valuable in battle.
- In the Thriller Bark arc of One Piece, fire was noted to be a particular weakness to the zombie mooks there, to the point that, specifically to combat attempts to exploit it, the General Zombies carried buckets of water around with them.
- 2000 AD:
- Fiends of the Eastern Front: Hans tries to destroy the vampiric Captain Constanta with a flamethrower while he's still sleeping in his coffin. It's not enough.
- Judge Dredd:
- During the "Judgment Day" arc, the Mega-City One Judges have to set their own city wall on fire to delay the invasion of zombies from the Cursed Earth.
- Subverted in the case of the Dark Judges, who can only be slowed down by the Lawgiver's incendiary bullets (and Judge Fire is obviously immune). It will destroy the host body, but their spirits can then roam free to find a new one.
- Child of the Storm:
- It's the most reliable way to kill the veidrdraugar, Norse super-zombies. Harry Dresden uses this quite a lot (and is mentioned to have used it on Red Court vampires as well), partially because it's so effective and partially because, well, he's Harry Dresden.
- Harry Thorson takes up this habit in the sequel, Ghosts of the Past, as part of his general habit of Playing with Fire, using it on Grey Court vampires (classic Dracula types — Red Court are Mayan demons, though just as flammable).
- In Luminosity, as in the text it's based on, burning is the only way to consistently kill a vampire.
- In The Carpenter, it turns out damaging the house causes the ghostly and homicidal carpenter pain. So, the film ends with the protagonists burning the place down, causing the carpenter to burst into flames, and burn away to nothingness.
- Freddy vs. Jason: Subverted when a teenager tries to kill Jason by drenching him with high-grade alcohol and igniting it. It only pisses Jason off, and the teenager is instead pursued by a flaming undead killing machine.
- Jason X: In the end, this is the only way that Jason is successfully put down, albeit in a particularly roundabout manner: the Space Marine captain performs a Heroic Sacrifice by grabbing hold of Jason and dragging him into the orbit of a planet, both burning up completely before they hit the surface.
- A Nightmare on Elm Street: Post-death Freddy Krueger has been set on fire as a way to dispose of him more than once. Whether he stays dead is another matter, but it's definitely karmic given that this is the way he died in the first place.
- At the end of Night of the Living Dead (1968) and its 1990 remake the zombie bodies are burned so they won't re-reanimate.
- In The Return of the Living Dead, Burt Wilson and Ernie Kaltenbrunner decide to burn the yellow zombie in the crematorium, since Removing the Head or Destroying the Brain and cutting it up didn't kill it. This, however, goes wrong. The soot from the burn mixes with rain, animating everyone in the local graveyard, who then go on a killing/zombifying spree. Cue the Zombie Apocalypse! Electricity would have done the job better.
- In Zoltan, Hound of Dracula, Inspector Branco burns the bodies of all the vampires he stakes and then scatters the ashes.
- Many of the admittedly extremely varied world folklore about vampires feature either an aversion to fire, or immolating the vampire's remains as the final step in destroying it for good.
- The vampires in numerous works of Gothic literature — including Carmilla, Varney the Vampire, and Dracula must be destroyed with fire after they're staked and decapitated. The fact that Dracula's body is not burned when he's killed in the original novel is often cited as a reason for latter-day authors to bring him Back from the Dead. Again.
- The first book in the Anita Blake series has a mention that flamethrowers work quite well on vampires.
- In P.C. Hodgell's Chronicles of the Kencyrath, fire is the best way to kill the shapeshifting, vampiric Changers, which are hard to kill but whose blood is very flammable. It's also the best way to kill the zombielike Haunts.
- Fire is one of two certain ways to kill a werewolf, the other being silver (though dismemberment is also implied to do the job — but only if it's extremely thorough) — werewolves being considered undead in the setting. It's also said to be effective against vampires, but they have such a grab bag of strengths and weaknesses that it's not nearly as reliable, and other methods are generally easier.
- Zombies are very strong, immortal and able to sew themselves back together if need be. However, the older they get, the drier they get, and so they're understandably nervous around fire.
- In The Dresden Files: Ghost Story, Harry explains in his Internal Monologue that fire works on pretty much everything, which is why he originally started using it as his preferred combat spell in the first place. It will even kill wandering ghosts, which are almost impossible to even interact with in the mortal world. Later, he mentions that fire has a spiritual cleansing effect, which is what allows it to work so well on dark magic.
- Eyrbyggja Saga: To stop the ravages of the undead Thorolf Twist-Foot, Thorodd has Thorolf's corpse dug up and burnt on a pyre. This puts an end to Thorolf's hauntings; however, a cow which licks up the ashes of the pyre later gives birth to a possessed bull-calf.
- "The Ghost of Philinnion": The citizens of Amphipolis resolve to burn the body of Philinnion, a young woman who has left her tomb to consort with a young man, to prevent her from coming to life again.
- Discussed and invoked in Harry Potter and the Half-Blood Prince, where Dumbledore explains that, since the dead are creatures of darkness and cold, their greatest fear is fire. Dumbledore then uses a ring of fire (in the movie, it became a full-on firestorm for Rule of Cool/visual effects purposes) to keep them away from Harry.
- In the Old Kingdom, Dead Hands and other minor Dead creatures need to have their bodies completely destroyed in order to be stopped, and fire is the best mundane way of accomplishing this. It's less effective against the more powerful forms of Dead, who exist primarily as spirit and don't necessarily need the specific corpses they're attached to (or, for the most powerful, and body at all). Cremating the fallen is also the accepted way of preventing them from rising as the Dead in the first place throughout the Kingdom and adjacent lands.
- The Saga of Erik the Red: Thorstein Eriksson comes temporarily alive again to reveal that the true cause of the plague in Lysufjord is the ghost of the overseer Gardi, the first man to die that winter in Lysufjord, and that Gardi's corpse must be burnt to stop the epidemic.
- Fire is the best way to take care of the wights in A Song of Ice and Fire. They can also be hacked to pieces, but fire is much easier. The only body part of a wight in the series not destroyed by fire remained animate until it rotted away.
- In The Sookie Stackhouse Mysteries, vampires are highly vulnerable to flame, to the point where matches will make some flinch.
- Twilight vampires are only able to die if another vampire tears them to pieces and then all of the pieces are burned. Even if they have been Driven to Suicide, this is absolutely the only way they can die, which is why Edward Cullen asks the Volturi to do this to him in New Moon. It's worth noting that Carlisle failed to try immolation during his many attempts at killing himself after he became a vampire, despite his father being a pastor who believed in wiping out evil supernatural creatures in such a manner.
- Fire is the only reliable way to kill the undead in The Witch Watch. That and just cutting their heads off and living them powerless and underground whilst still being conscious.
- Discussed and averted in The Zombie Survival Guide, which advises that fire is a poor weapon to use on zombies: they aren't afraid of it and can't feel pain, it won't stop them until they're literally cooked, and in the meantime you're being attacked by a flaming zombie instead of a regular one.
- Buffy the Vampire Slayer and its spinoff, Angel, both feature vampires who can only be killed in five ways, one of which ways is setting them on fire and burning them to dust.
Dawn: If you touch my sister, hurt her in any way... you're going to wake up on fire.
- In Game of Thrones this is the most effective way to kill the wights created by the White Walkers from the humans and other animals who die fighting them.
- A group of revenants disintegrate upon contact with fire in an episode of Hercules: The Legendary Journeys.
- In Supernatural a common solution to the Monster of the Week, if it's a ghost or other formerly-alive being, is to find and burn its corpse and/or bones, which utterly destroys it on this plane. Kill It with Fire tends to be the default solution from the Winchester brothers against monsters they don't know much about, and it's usually a safe bet (for example against Nazi Necromancers in "Everyone Hates Hitler").
- The Whoniverse:
- Doctor Who:
- In episode 42, if you looked into the living sun its soul entered your body and you effectively became undead, leaving you with only two ways to die: the soul could burn you from the inside out, or it could eat you.
- The Family of Blood's scarecrows are undead and must be burned.
- In Torchwood: Miracle Day, nobody can die. It is impossible and so the government of Britain decide that, when the hospitals get too full, anyone who should be dead is to be incinerated. Cutting their heads off and being squashed and burnt beyond recognition and given the lethal injection didn't kill them, so turning them to ashes is apparently better. The ashes may still be living, but they're not human, so the government decides it's fine to throw them away.
- Doctor Who:
- Arduin RPG, The Compleat Arduin Book 2: Resources. The Drich undead takes 50% more damage than normal from fire.
- Dungeons & Dragons:
- Fire is extremely useful against most undead, who are often immune to a wide variety of attack modes.
- Early editions had mummies susceptible to fire damage — justified by real-world (and completely dead) Egyptian mummies being covered in flammable resins. One of the Grimtooth's Traps books combined this with Taking You with Me, by stuffing a mummy with a nice big keg of gunpowder.
- In 3rd Edition, a number of fire, light and sun-based attack spells have extra effects against undead, such as wall of fire inflicting double damage to them. Notably this is not due to "holy power" being mixed in, as usual for anti-undead spells; fire hurts undead regardless of whether its source is good or evil. However the Deathless, Good Counterparts of undead, do not take extra damage from these spells.
- In the New World of Darkness, fire just deals lethal damage to mortals and those not vulnerable to it. Vampires, Prometheans, and mummies all receive aggravated damage ("OW MY VERY BEING IS RENDED") from fire, however (Vampires and mummies because they're desiccated corpses held together and made lively by magic, and Prometheans because the "Divine Fire" that gives them life overloads when exposed to fire). And the Mekhet clan vampires take double damage from fire.
- Old World of Darkness:
- Vampires in Vampire: The Masquerade take aggravated damage (very difficult to heal) from fire as well as sunlight. These two substances are the main ways to truly kill a vampire (devouring their soul also works, but only another vampire can do it). Vampires of the Setite clan are especially weak to fire, taking double aggravated damage from it. In Werewolf: The Apocalypse the shapeshifters, which generally hate vampires, have developed various magic abilities specifically to take advantage of this weakness.
- The Vampire: The Masquerade/Mage: The Ascension crossover supplement "Time of Thin Blood" saw the Technocracy respond to the rising of the Ravnos antediluvian in Bangladesh by declaring Code Ragnarok... and then beating the shit out of the ancient vampire by setting him on fire with orbital mirrors after nuking him from orbit with nukes enhanced by Awakened Science. Up to that point, everything else that various supernatural groups (i.e. Garou werewolves, Asian vampires) had thrown at Ravnos had been ineffective. So, yes, on that day, the much-maligned Technocracy saved the world. Take That!, mages.
- Fire is generally one of the best attacks to use against undead in Battle for Wesnoth — it at the very least reliably targets one of their weaker resistances, and several undead units actually take additional damage from it.
- Directly contradicted in the survival horror MMORPG Dead Frontier, where, in both the lore and the gameplay, not only does fire not kill zombies permanently, it makes them even stronger.
- Few undead in Dominions are resistant to fire, and vampires especially are weak to it. Fire magic is also a large source of anti-undead spells.
- In Dragon Age: Origins when you get to the town of Redcliff you discover that it's being attacked by undead every night. While exploring the town and working to shore up the defenses, you can find a large stock of lantern oil in an abandoned general store, which you can recommend be used as a defense. If you do so, a large bonfire will be constructed on the road into the town that the undead are attacking from, slowing them down and causing significant damage to them.
- Subverted in Dwarf Fortress. While Magma Keeps It Dead is a viable solution for corpses that might otherwise reanimate, currently active undead can survive being on fire indefinitely unless killed off properly.
- In The Elder Scrolls series, fire-based spells and enchantments are extremely effective against most types of undead, including otherwise magic resistant types of undead like vampires and liches.
- Mantorok (dried husk) and Xel'lototh (mummy) zombies in Eternal Darkness can easily be killed by fire.
- In many Final Fantasy games, Fire- and Holy-elemental spells are common weaknesses of Zombie-type enemies. Black Mages typically learn a simple Fire spell early in the game to make short work of undead monsters, but Holy magic is often a high-tier White Magic spell not learned until the end of the game, so White Mages often have to rely on healing magic to cause damage.
- In Half-Life, using gas canisters or oil drums to set zombies on fire is a pretty effective way of killing them. Especially used in the Ravenholm level of Half-Life 2, along with fire traps. (Setting zombies on fire is also a convenient way to light up dark areas, if you're heartless enough to listen to the human puppets being controlled by the headcrab screaming and screaming in horrible agony...
- Judge Dredd: Dredd vs. Death: The game will punish you for using the Lawgiver's incendiary bullet on regular perps, but vampires and zombies are fair game.
- Fire from your molotov cocktails in Left 4 Dead is extremely valuable against the infected. The moment a common infected is set on fire, they are instantly killed. Special infected won't die immediately if set on fire, but unless they can find a pool of water to jump into, they will burn to death. Setting a Witch on fire is considered to be less risky than trying to crown her since a burning Witch moves slower, thus buying you time to get away or pump her full of bullets. The sequel adds incendiary ammo as another method to burn zombies with.
- Vampires in the Legacy of Kain series can only be killed by four things: water, impalement, sunlight, and fire. In the first Soul Reaver, the Fire Reaver can shot projectiles that one-hit kills them.
- In Middle-earth: Shadow of War, undead uruks or ologs gain the trait of being Weak to Fire if they are nemeses.
- The zombies in Nox will resurrect indefinitely upon being killed, unless killed with a fire spell or a fire-enchanted weapon.
- The skeletal Dry Bones in Paper Mario can only be removed from a fight using fire-based attacks, to which they are particularly vulnerable. The explanation given is that burning them means there's nothing left to be reassembled. Curiously fireballs have little effect on Dry Bones in other games of the Super Mario Bros. franchise the best answer to them is in fact ice* .
- This is true for the MMORPG Ragnarok Online, where fire will deal up to 200% damage against undead enemies. Fire elemental weapons and spells can also be used against ghost enemies to deal 100% damage (unlike the "normal" element, dealing only 25% or even 0% damage).
- Red Dead Redemption: Undead Nightmare does this. You can even burn the coffins that are making the zombies rise up from the ground. It usually takes a hit or two from a torch to make a zombie fall.
- The zombies in the Resident Evil games are vulnerable to fire.
- In Resident Evil 5, Uroboros plays this absolutely straight. The best way to kill the first boss, which just so happens to be a mass of Uroboros? Incinerate it in the conveniently placed furnace where the fight takes place. Bonus points for the window that lets you watch as the creature is immolated. Also, you can use incendiary grenades and flame ammo for the Grenade Launcher. While they aren't super-awesome Majini killers, setting those walking sacks of diseased flesh who are looking at you funny on fire really helps, and if they are far enough away then they will die before they get to you.
- Fire is generally the best way to prevent Crimson Heads, given that the tried and true tactic of aiming upwards with the shotgun is no longer a guarantee of head removal.
- In the Shining Force games fire-based magic attacks are very effective against zombies.
- The zombies in Skylanders: Spyro's Adventure can only be damaged by fire-based attacks. If you don't have a Fire-type Skylander, you can damage them by pushing candles into them. (In the sequel, you don't need fire, but it makes things easier.)
- In Total War: Warhammer, being undead doesn't inherently cause vulnerability to fire, but it's usually most effective against undead factions. It deals extra damage to creatures with regeneration, which the vampire counts faction is stuffed with, and to the mummified tomb king heroes and lords, while the ethereal creatures that are found mostly in the vampire counts and vampire coast have massive physical resistance but low health and die fast against magic or fire damage.
- In Warframe, the Infested are vulnerable to fire damage.
- The best way to kill Zombies in the XCOM series are with Incendiary/Phosphorous rounds, since these will automatically kill the Chryssalids/Tentaculats inside them.
- In Hungry City, that's one of the only ways to kill a zombie (the other being removing the head as usual) but when a vampire is set on fire, he just puts it down with his powers and is unharmed.
- The Order of the Stick:
- Alluded in the prequel, On the Origin of PCs. When Roy recruits Vaarsuvius into the order, he mentions that the elf is an expert at fire magic, which will be useful since he's expecting to fight lots of undead in their upcoming quest.
- Fittingly for her patron deity (Loki, the God of Flames and Chaos), during a fight with vampires Hilgya Firehelm conjures a searing column of fire to take them down. The spell lacing flames with holy energy, the magic protecting the undead from fire is much less efficient.
Blackwing: Watch out, Hilgya — they're protected against fire stuff!
Hilgya: Not a problem — Loki's fire burn hotter. Empowered Flame Strike.
- In Trope Overdosed The Webcomic, while doing some Level Grinding, Alice has burned lots of zombies
- In the Darkwing Duck episode "Night of the Living Spud", a redneck decides to test how flammable a vampire is.
Zeke: [strikes a match] Zack... get the diesel fuel.