Killer Space Monkey

Maybe it's because they land somewhere in the Uncanny Valley. Maybe, as with the Monster Clown, it's because writers like subverting the traditionally "cute". Maybe it is a reflection of our savage ancestry. Maybe it's a remnant of our struggle with our differently-evolved cousins. Or maybe it's simply that Everythings Better With Monkeys. Whatever the reason, killer simians make for good alien monsters.

Such extraterrestrial monkeys tend to be brutish killing machines - an intelligent alien ape is usually a subversion.

Yes, we know this should be called Killer Space Non-Human Primate. No, Earthly villains who happen to be actual apes are not Killer Space Monkeys.

See also Maniac Monkeys. Not to be mistaken with Apes in Space, who are monkeys that go into space.

Anime and Manga

 * The Saiyans from Dragonball Z. They used their power to transform into giant "apes" during the full moon to conquer planets for Freeza. And calling the saiyans 'monkeys' was a bit of a racial slur used by Freeza and his underlings.

Comic Books

 * The Thunes in Mike Baron and Steve Rude's comic book Nexus resemble apes. Thunes are an intelligent race, though, and are just as varied morality-wise as humans. The two most prominent Thune castmembers are Nexus's two best friends, Dave and his son Judah.
 * The Marvel Transformers Generation 1 comic had a race of (somewhat) intelligent, vicious cyborg monkeys living in limbo.
 * A group of intelligent killer space monkeys appear in the Doctor Who Magazine strip "Sins of the Fathers".
 * Titano from the Superman comics, who features in the page image, started life as an ordinary Earth ape. Rocketed into space, he and his ship were bombarded with radiation, which changed him into a giant ape with incredible strength and the ability to emit beams of Kryptonite radiation from his eyes.

Film

 * One variation is the movie Planet of the Apes, in which the apes are exactly as brutish and nasty as humans.
 * The aliens in Evolution start evolving into ape-monsters around the third act of the film as they reach the monkey stage of the evolutionary "ladder".
 * The Morlocks in the 2002 adaptation of The Time Machine were particularly ape-like.
 * Star Wars gives us Chewbacca and his fellow Wookies, who are for the most part the most unambiguously noble critters in the galaxy. The Wampa from Hoth is a more traditionally monsterish version.
 * The Simeons in the Godzilla series were a race of apes from a planet that was coming close to being sucked into a black hole, deciding to relocate themselves to Earth and building Mechagodzilla to try and conquer the planet.

Literature

 * Larry Niven's Known Space setting has multiple hominids evolved from the Pak, including a whole Ring World full of sentient and non-sentient types. The Morlocks of Wunderland are also apelike cave-dwellers.
 * John Carter of Mars has the White Apes - gigantic, four-armed Martian primates.
 * In After Man a Zoology of The Future, several species of deadly predator have evolved from monkeys, including the fish-eating swimming monkey, the cheetah-like horrane, and several species of carnosaur-like raboon.

Live Action TV

 * The Ogrons, a race of mercenary grunts often turning up as henchmen to the Daleks in Doctor Who.
 * The Kromaggs, the product of parallel evolution on one of the worlds of Sliders with a taste for human eyeballs. In their initial appearance, they were most definitely ape-descended, though later appearances made them more human, with something of a Nosferatu bent. (Note that their name comes from "Cro-Magnon", but the actual Cro-Magnons were modern humans.)
 * The Magog from Andromeda.
 * Big Bad Pearl Forrester acquired a killer space monkey named Professor Bobo as a henchman in later seasons of Mystery Science Theater 3000. He... wasn't particularly good at his job.
 * Firefly: Space monkeys are raised as a possible reason why Kaylee's engine room is so untidy in "Train Job".
 * Goldar of Mighty Morphin Power Rangers fame.
 * The Mugato from Star Trek the Original Series.

Other

 * An Easter Egg in Adobe Photoshop CS 2 enables you to bring up an alternate about box, (very temporarily) relabeling the program "Adobe Space Monkey".

Tabletop Games

 * Not so much killer, as their role is more of The Engineer, but Warhammer 40000 features the Jokaero, a race of space orangutans.
 * Another tabletop wargame, AT-43, features a race of intelligent apes (actually uplifted Earth gorillas), fond of philosophy and simian-related Shout Outs.
 * Star Frontiers had the Yazirians as a playable race. They were generally good guys, of the Proud Warrior Race Guy sort.
 * Spelljammer brought the Yazirians back, but renamed them "Hadozee," or "deck apes."
 * Alternity had the Weren, who were also Proud Warrior Race Guys.

Video Games

 * System Shock 2 had creepy zombie space lab monkeys. With Psychic Powers (either cryokinesis or pyrokinesis, depending on which kind of monkey).
 * City of Heroes has transdimensional psychic monkeys. Which emit toxic gas when defeated.
 * And gives you a badge for "arresting" 1000 of them.
 * While both the Grunts and the Elites from the first game have a substantial number of ape-like features, Halo 2 went right out and admitted it with the Brutes, who are basically gorillas. Gorillas in Powered Armor who dual-wield shotguns. Yeah.
 * The Covenant name for Grunts is Unggoy, which in Tagalog means monkey.
 * Halo Reach has a Giant Space Flea From Nowhere encounter with a pair of giant tusked lizard-monkeys.
 * The Cosmic Silverback in the Dead Ops Arcade minigame of Call of Duty Black Ops, along with the much smaller Space Monkeys in the Nazi Zombies map Ascension.
 * A literal case with General Skun'ka'pe in the third season of the Sam and Max episodic adventure game.
 * The Tarka from Sword of the Stars are one part reptile and one part this. In return, they consider us this too.
 * The Purr-Lin in the Turok series.
 * Kuja from Final Fantasy IX.

Western Animation

 * Captain Simian and The Space Monkeys had as its main cast a group of good guy space monkeys. The Big Bad, meanwhile, had an evil cyborg space monkey after them, RHESUS-2.
 * An odd twist on the trope is the Super Robot Monkey Team Hyperforce Go. They're technically the good guys, but they have no compunction whatsoever against killing their enemies, and being brutal about it.
 * Bucky O Hare and The Toad Wars: "Beetleguizean Berzerker Baboon! Run away!"
 * An episode of Superman the Animated Series has Titano (see Comics section) as Lois Lane's pet monkey (her father was part of NASA at the time.) He eventually lands in Metropolis, starts growing to massive size and runs amok downtown.

Web Comics

 * The Lespuko from El Goonish Shive probably counts as this. It is a species of alien, its name means "Rock Ape" and it has been shown to be aggressive.

Real Life

 * There are apes (and other animals) in satellites within Earth's orbit. They are the test subjects in mostly US and former USSR space exploration research. They were sent up to monitor the effects of such an environment on living things. They were left up there. Only they are most likely to have been killed instead of mutated into killer space monkeys. :-(