Immortality

Immortality, living forever, is a trope found in many fannish sources. Immortality may be an inherited racial characteristic; alternatively, it may be acquired by accident or mutation, or by deliberate intervention using magical, alchemical or technological means. Some immortal figures are invulnerable to injury, possess rapid healing or regenerative abilities, or return from death indefinitely. Others can be killed (sometimes particular methods are required) but do not naturally die of old age. Immortality is often accompanied by lack of aging, or extremely slow aging. 
Becoming immortal has been a goal of characters since the Epic of Gilgamesh. The downsides of immortality, such as boredom leading to apathy, everyone dying on you & inability to adapt to change, are often explored. It's not surprising that a quest for death is one common theme. Another theme is the difficulty of forming relationships where only one character is immortal. Many fanworks use immortal characters to illuminate scenes in human history, with the crucifixionSpike: "If every vampire who said he was at the crucifixion was actually there, it would've been like Woodstock." School Hard episode quotes at IMDB, WW1 trenches & the moon landing often being chosen. Immortality can also help characters to function as a panfandom Little Black Dress. A version of this trope seen in many fandoms is the idea of an immortal child, permanently staying the same age (usually prior to puberty). Some remain child-like, others are "old souls" in young bodies, often twisted and resentful of being treated as children.
==Cross-fandom Concepts==
*Angels, demons
*Anthropomorphic personifications
*Brain uploads, brain in a jar
*Cyborgs, robots, sentient AIs
*Deities, god-like beings
*Elixir of Life, Philosopher's Stone
*Elves
*Fairies, the Fey
*Ghosts
*Golden or silver apples
*Groundhog Day-type time loops
*Nanites
*Norse Mythology/MCU: Marvel characters are granted Golden Apples (Apples of Idunn) to make them immortal.
*Phoenix
*Regeneration
*Souls in the afterlife
*Vampires
*Zombies and the Undead
==Fandoms with Immortal Characters or Races==
*Achievement Hunter: The lack of consequences for death in video games makes this common in GTA or Minecraft-based fics, and Immortal Fake AH Crew is a popular fandom trope.
*The Addams Family (all versions): Wednesday appears to have been a child for a very long time.
*American Gods: gods
*Angel/Buffy the Vampire Slayer: vampires, the Immortal, hell-gods, possibly Dawn Summers
*Baccano!: elixir of life
*Battlestar Galactica: Cylons (if a resurrection ship is in range)
*Blade of the Immortal: Manji
*The Borribles (Michael de Larrabeiti); Immortal children roam London in tribes living by their wits.
*Captain Scarlet and the Mysterons: Captain Scarlet, probably Captain Black (but it isn't clear if he can recover from destruction spontaneously, or needs Mysteron intervention).
*Dark is Rising: Old Ones
*DC Comics: Numerous characters including gods and demigods, Vandal Savage (a caveman mutated by meteor radiation), Jason Blood (a knight who was cursed and shares his body with a demon), Ra's al Ghul (Periodical immersion in an alchemical Lazarus Pit), etc.
*Diana Wynne Jones: several novels have immortal characters, including the Dalemark Quartet, Dogsbody & Eight Days of Luke
*Despicable Me: In the third film Gru says of Margo "She looks twelve. She will always be twelve." While this may be simple denial, given the mad science seen in this series it is possible that she has received some form of immortality treatment.
*Discworld: Discworld features many gods, vampires, and even anthropomorphic personifications. The character of Death (Discworld) is a very prominent figure and often has to grapple with immortality in his books. Death (Discworld Sub-Series)
*Doctor Who: Cybermen and several alien races. Most notably, Time Lords live for thousands of years via longevity and regeneration. Captain Jack Harkness is a well known and popular immortal character in the series.
*Dogma: angels, God, the Metatron
*Forever: Dr Henry Morgan, "Adam"
*Forever Knight: Nick Knight and other vampires
*Girl Genius: Jagers (dead soldiers brought back to life by weird science) are immortal, or at least age VERY slowly. Several other characters appear to have indefinitely prolonged lives.
*Good Omens: angels, demons, the Metatron
*Greek Mythology: gods, demigods
*Harry Potter: horcruxes, elixir of life
*Hebrew Bible: God, Lucifer, angels
*Robert A. Heinlein: Extended lifetimes by selective breeding, later by bio-engineering etc. in the Lazarus Long books.
*Hercules: The Legendary Journeys: gods, demigods, possibly Hercules
*Highlander: Immortals
*The Hitchhiker's Guide to the Galaxy: Wowbagger 
* Larry Niven's Known Space series: Several forms of immortality treatment are widely available, at first via transplants and cloned organs, later by the drug Boosterspice which halts aging.
*Lois and Clark: Superman was believed to have a greatly extended life due to his "energy field" but depleted it (to an unknown extent) to save Jimmy Olsen.
*Lovecraft: Great Old Ones
*Marvel Comics; numerous characters are effectively unkillable or have (or appear to have) extended life spans as a result of mutations etc., most notably Wolverine; Deadpool; various gods and demi-gods; numerous characters who are implied to age slowly if at all for other reasons including Steve Rogers, Bucky Barnes, Bruce Banner etc.
*Narnia: Aslan, Jadis
*New Amsterdam: John Amsterdam
*Nine Princes in Amber and sequels by Zelazney: Most of the major characters are immortal dimension-hopping Princes and Princesses, capable of altering reality.
*Norse Mythology: Aesir, Vanir, Jotunn. In some versions of the legends Idun's apples can be eaten to become immortal.
*The Old Guard: all five of the title characters are immortal warriors who, for reasons unknown to them are unable to die and do not age. 
*Percy Jackson and the Olympians: gods, demigods
*Peter Pan (all versions); Peter and the Lost Boys do not age so long as they wish to stay in Never-Never Land.
*Sanctuary; Doctor Helen Magnus, various Abnormals, vampires.
*Sandman (Vertigo comics); The Endless, most supernatural beings, Hob Gadling and other human immortals.
*The Shadowhunter Chronicles: warlocks, fairies, vampires, angels and greater demons.
*Spirited Away: Haku
*Stargate SG-1: The Asgard are effectively immortal via cloning and memory transfers, but gradually declining due to copying errors. The Goa'uld and Tokra achieve very long life-spans by symbiosis with humans (and other suitable species), moving from one host to another when age begins to affect the body.
*Star Trek: many immortal and long-lived races including the Q, Organians, the Borg hive mind, etc.
*Supernatural: angels, demons
*Tolkien: Elves, Valar, Maiar, Wizards, Ring-bearers
*Top Gear: Arguably The Stig, though Black Stig was "killed off" and replaced by White Stig.
*Torchwood: Jack Harkness, Owen Harper, Miracle Day
*True Blood: vampires
*John Varley: Immortality via cloning and memory transfer in most of his novels. It is usually shown as illegal unless the clone is a replacement of the original person, with a duplicate person normally illegal unless there are extenuating circumstances.
*Vorkosigan Saga: Immortality via cloning and brain transplants - classed as murder on most worlds since the cloned body has a mind of its own before surgery. Also biochemical and genetic longevity treatments.
*Watchmen: Doctor Manhattan
*Who Framed Roger Rabbit?: Toons appear to be immortal unless Dipped.
*The X-Files: canonically it's been heavily implied that Dana Scully may be immortal, see Scully is immortal
*Xena: Warrior Princess: gods, demigods
*For more of the many fandoms with vampires, see the list in that article
==Example Fanworks==
*Buffy the Vampire Slayer: Rough Heals by Voleuse. One of several immortal-Dawn stories set in the Firefly universe
*Buffy the Vampire Slayer: Resurrection by Littlerhymes. Spike & cyborg-Buffy in the future
*Buffy/Torchwood: My Immortal by Elisi. Captain Jack Harkness is The Immortal, a mysterious figure in the Buffyverse.
*Dalemark: Allow For Inflation by Aria. Mitt/Maewen; the difficulties of relationships with an immortal 
*Greek Mythology: Small Step For Man by Toft. Artemis & Apollo through human history
*Harry Potter: Alone and Palely Loitering by Squibstress. The Flamels and the centuries of marriage the Elixir of Life gives them
*Harry Potter: The Cost of Living by Sansa. Fallout from the fall of Voldemort makes Harry & Snape immortal
*The Lord of the Rings: Back to the Beginning by Adina. Legolas/Gimli; an unusual take on the relationship between an immortal and a nonimmortal
*The Silmarillion: Firimar by Ithilwen. An Elf observes the moon landing
*Spirited Away: Becoming by Springgreen. Haku's origin story
==References==
Category:Glossary