According to popular cultural, there are several tried & true methods of raising the living dead, i.e. create zombies.
It's interesting how over time, these explanations of where zombies came from changed between (voodoo) magic, evil scientists, demonic curses, nuclear weapons, chemicals and pesticides, aliens, bioweapons, virusses and sicknesses, with the odd case of crashed meteorites or even sheer force of will.
There are also those films who don't supply an explanation at all; i.e. the explanation you get is that people become zombies by getting bitten by zombies (duh) without explaining where the first zombies came from, although these examples are harder to find than you might expect in the zombie genre.
Additions are welcome. I am trying to limit the number of movies with identical explanations and limit it as much as possible to cases that are at least marginally different from other films in some small way.
An obsessed scientist assembles a living being from parts of exhumed corpses. (70 mins.)
“ Method: a mad scientist combining different dead body parts to build a new man, bringing it to life with lightning.
Granted, it is arguable whether Frankenstein is a real zombie. He is reanimated of course, and he is also slow, hulky, very strong, and he makes zombie-like noises instead of speaking. But we aren't lead to believe that he is especially hard to kill in the way most zombies are, and he is also more misunderstood than he is malevolent. He doesn't attack people to eat them, and we aren't lead to believe that if he would bite people, that this would have some sort of contaminating effect.
On the other hand he may just be different than modern zombies because this is the oldest film in this list, and it does make sense to see him as a proto-zombie, or the ancestor of all modern zombie stories. ” - RagingR2
A young man turns to a witch doctor to lure the woman he loves away from her fiancé, but instead turns her into a zombie slave. (69 mins.)
“ Method: a failed attempt to use magic to win another one's love ” - RagingR2
Things to Come
The story of a century: a decades-long second World War leaves plague and anarchy, then a rational state rebuilds civilization and attempts space travel. (100 mins.)
“ Method: the 'wandering sickness' causes people to walk slowly and insensibly ” - RagingR2
I Walked with a Zombie
A Canadian nurse is hired to care for the wife of a sugar plantation owner, who has been acting strangely, on a Caribbean island. (69 mins.)
“ Method: Voodoo magic ” - RagingR2
The Mad Ghoul
A university chemistry professor experiments with an ancient Mayan gas on a medical student, turning the would-be surgeon him into a murdering ghoul. (65 mins.)
“ Method: a chemistry professor experimenting with an ancient Mayan gas.
Ehm... 'an ancient Mayan gas', what the heck is that? Sounds like the writers had chemistry and the occult mixed up. :) ” - RagingR2
Japanese spymaster Prince Daka operates a covert espionage organization located in Gotham City's now-deserted Little Tokyo which turns American scientists into pliable zombies. (260 mins.)
“ A Japanese mad scientist turns people into 'electronic zombies'.
How...? Not really an explanation. ” - RagingR2
I Eat Your Skin
A cancer researcher on a remote Caribbean island discovers that by treating the natives with snake venom he can turn them into bug-eyed zombies... (84 mins.)
“ Method: snake venom ” - RagingR2
The Last Man on Earth
When a disease turns all of humanity into the living dead, the last man on earth becomes a reluctant vampire hunter. (86 mins.)
“ Method: a bacteroid disease (plague) ” - RagingR2
A crazed female scientist uses nerve gas to turn local teenagers into her unquestioning slaves. (73 mins.)
“ Method: nerve gas ” - RagingR2
Plan 9 from Outer Space
Aliens resurrect dead humans as zombies and vampires to stop humanity from creating the Solaranite (a sort of sun-driven bomb). (79 mins.)
“ Method: aliens executing 'Plan 9' to prevent humanity from creating a doomsday weapon ” - RagingR2
No Survivors, Please
Aliens attempt to take over the Earth by taking over the bodies of humans at the moment of their death, and using them as tools for their invasion plans. (93 mins.)
“ Method: possession by aliens ” - RagingR2
The Plan - to build a super human; How? - by murdering innocent convenient victims and using various bits of them; The Result - Creatures on the rampage. (91 mins.)
“ Method: a failed attempt to build superhumans from body parts ” - RagingR2
“ Method: radiation from a fallen meteorite ” - RagingR2
In 1906, in China, a British anthropologist discovers a frozen prehistoric creature and must transport it to Europe by train. (84 mins.)
“ Method: an ancient man found frozen in ice is host to an extragalactic evil presence, that sucks peoples learning and memories out of their brains through their eyes. ” - RagingR2
Tombs of the Blind Dead
In the 13th century there existed a legion of evil knights known as the Templars, who quested for eternal... (101 mins.)
“ Method: presumably drinking human blood and making sacrifices to the gods.
Knights templar who drank human blood and made sacrifices in the 13th century questing for eternal life were subsequently punished to death for their crimes, and are now ressurected. It is a bit unclear whether in the end it was their blood drinking and sacrificing that was succesful after all, or the punishment that they got for that, or another factor altogether that brought about their resurrection. ” - RagingR2
The Dead Are Alive
A photographer on an archaeological expedition digging up Etruscan ruins in Italy begins to suspect that not all the Etruscans buried there are actually dead. (105 mins.)
“ Method: presumably people getting burried underneath ancient ruins
In other words: no real explanation is given. ” - RagingR2
The Death Wheelers
A gang of young people call themselves the Living Dead. They terrorize the population from their small town... (85 mins.)
“ Method: a pact with the devil to return yourself as a living dead ” - RagingR2
Vengeance of the Zombies
An Indian mystic uses magical chants to raise women from the dead, then sends them out to perform revenge killings for him. (89 mins.)
“ Method: an Indian mystic reciting magical chants ” - RagingR2
The Living Dead at Manchester Morgue
A cop chases two hippies suspected of a series of Manson family-like murders; unbeknownst to him, the real culprits are the living dead, brought to life with a thirst for human flesh by chemical pesticides being used by area farmers. (95 mins.)
“ Method: pesticides used by local farmers ” - RagingR2
The Grapes of Death
A young woman discovers that the pesticide being sprayed on vineyards is turning people into killer zombies. (85 mins.)
“ Method: pesticides ” - RagingR2
Dawn of the Dead
Following an ever-growing epidemic of zombies that have risen from the dead, two Philadelphia S.W.A.T. team members, a traffic reporter, and his television executive girlfriend seek refuge in a secluded shopping mall. (127 mins.)
“ Method: no explanation at all, i.e. the zombies were just there to begin with.
Arguably, this is a sequel to the Night of The Living Dead, so the explanation is still the crashed meteorite from that film, although it recieves no mention in this film. ” - RagingR2
City of the Living Dead
A reporter and a psychic race to close the Gates of Hell after the suicide of a clergyman caused them to open, allowing the dead to rise from the grave. (93 mins.)
“ Method: opening the gates of hell ” - RagingR2
After drug crops are sprayed with a chemical by a passing airplane, the growers of the crop are poisoned... (89 mins.)
“ Method: weed-killing chemicals ” - RagingR2
The Evil Dead
Five friends travel to a cabin in the woods, where they unknowingly release flesh-possessing demons. (85 mins.)
“ Method: demonic possession ” - RagingR2
Kung Fu Zombie
A criminal comes to town in order to kill Billy Chong over a past dispute. But instead of getting his own hands dirty... (80 mins.)
“ Method: Tao magic ” - RagingR2
A dedicated student at a medical college and his girlfriend become involved in bizarre experiments centering around the re-animation of dead tissue when an odd new student arrives on campus. (104 mins.)
“ Method: a mad scientist reanimating the dead ” - RagingR2
The Return of the Living Dead
When two bumbling employees at a medical supply warehouse accidentally release a deadly gas into the air, the vapors cause the dead to rise again as zombies. (91 mins.)
“ Method: a chemical produced by the U.S. army. ” - RagingR2
A young man's mother is bitten by a Sumatran rat-monkey. She gets sick and dies, at which time she comes back to life, killing and eating dogs, nurses, friends, and neighbors. (104 mins.)
“ Method: getting bit by a Sumatran rat-monkey ” - RagingR2
Army of Darkness
A man is accidentally transported to 1300 A.D., where he must battle an army of the dead and retrieve the Necronomicon so he can return home. (81 mins.)
“ Method: screwing up the last word when trying to recite a magical phrase ” - RagingR2
My Boyfriend's Back
Missy McCloud is the most beautiful girl in school and Johnny Dingle has been in love with her for years... (85 mins.)
“ Method: sheer force of will; not wanting to die because you're in love ” - RagingR2
(1998 Video Game)
You play a scientist who must make his way through a ruined underground scientific complex infested with danger.
“ Method: infection by 'head-crabs', one of many kinds of monsters that came through a rift opened to another dimension when experiments in transportation technology went disastrously wrong ” - RagingR2
A group of young shoppers and employees must band together when a zombie outbreak over runs their Hong Kong shopping center in the middle of the shopping day. (94 mins.)
“ Method: experimental Iraqi biological weapon disguised as a soft drink ” - RagingR2
Only legendary Japanese garage rock band Guitar Wolf can stand between a race of aliens from destroying earth with an army of zombies. (98 mins.)
“ Method: alien invasion ” - RagingR2
There are 666 portals that connect this world to the other side. These are concealed from all human beings. Somewhere in Japan exists the 444th portal.... The forest of resurrection. (119 mins.)
“ Method: The evil spirit from the 444th portal to 'the other side' ” - RagingR2
Stacy: Attack of the Schoolgirl Zombies
Girls surrounding 17 years old are affected by an illness that make her to be 'Stacies': they feel a strange and momentary happiness until they become zombies. (80 mins.)
“ Method: a mysterious disease affecting 15 and 17 year old girls ” - RagingR2
A special military unit fights a powerful, out-of-control supercomputer and hundreds of scientists who have mutated into flesh-eating creatures after a laboratory accident. (100 mins.)
“ Method: The T-virus, a genetically engineered bio-weapon ” - RagingR2
28 Days Later...
Four weeks after a mysterious, incurable virus spreads throughout the UK, a handful of survivors try to find sanctuary. (113 mins.)
“ Method: a mysterious, incurable virus ” - RagingR2
Shaun of the Dead
A man decides to turn his moribund life around by winning back his ex-girlfriend, reconciling his relationship with his mother, and dealing with an entire community that has returned from the dead to eat the living. (99 mins.)
“ Method: waking up on the wrong morning
A.k.a. providing no explanation at all, the comedy way ” - RagingR2
After an experimental bio-weapon is released, turning thousands into zombie-like creatures, it's up to a rag-tag group of survivors to stop the infected and those behind its release. (105 mins.)
“ Method: an experimental bio-weapon ” - RagingR2
S.T.A.L.K.E.R.: Shadow of Chernobyl
(2007 Video Game)
You play as a scavenger suffering from amnesia inside the exclusion zone of a nuclear power plant in the Ukraine which exploded, creating mutants, and weird paranormal activity.
“ Method: nuclear disaster ” - RagingR2
Zone of the Dead
InterPol agents must join forces with dangerous prisoner to fight zombie hordes. (101 mins.)
“ Method: Biohazard created by ecological holocaust ” - RagingR2
The Last of Us
(2013 Video Game)
20 years after a pandemic destroyed the United States, Joel gets the task of taking Ellie into a nation-wide adventure to unveil a secret that can save humanity.
“ Method: Fungal infection ” - RagingR2
Deus Ex: Human Revolution
(2011 Video Game)
After a shadowy black ops team kidnaps several scientists security manager Adam Jensen was sworn to protect, he must harness the power of his new-found cybernetic augmentations to save their lives.
“ Method: (mechanical) body augmentations gone awry.
Note 1: A bit arguable whether they are zombies or zombie-like, but when playing this part of the game, they certainly reminded me of zombies in their erratic, unpredictable and agressive behaviour.
Note 2: There is no mention of nanobot augmentations in DE:HR, since chronologically, it precedes DE 1 & 2. ” - RagingR2