I previously talked about the notable fiendish apes of D&D, and now I'm going to summarize some the mortal(?) simian monsters of D&D (and some Pathfinder monsters too).
Based on Central American legends, the Ahuizotl is an ampihbious and very evil monkey-dog-thing with a claw on the end of its tail. Interestingly, the first D&D version of the Ahuizotl in the Maztica setting is more of an anthropomorphic crocodile.
Goat-horned temperate-environment cousins of the Yeti that look sinister as fuck. They are actually rather peaceful though.
Evil bat-winged baboons rumored to be from an parallel icy parallel world. They are practically immune to cold. From an obscure UK module called Dark Clouds Gather.
Despite their name, blood apes are actually peaceful sapient creatures: the name comes from their bright red fur. The alpha male of the a pack can use an "animal growth" ability on himself, perhaps the best phallic joke in all of D&D.
From Pathfinder. These guys are basically more upright and (barely) murderous versions of chimpanzees. They're advanced enough to make leather armor though.
It seems that someone was a big fan of the Gorilla-bear below and basically ended up copying it while adding in a brain-eating ability. Bravo, game designers!
Technically more like monkeys, these creatures have raccoon tails and leathery skin-flaps they use to glide/fly.
Law-abiding, common-speaking, sapient apes. Come on, 3rd party publishers, this is AD&D Fiend Folio-tier.
After the last sentence, I flipped through the AD&D Fiend Folio and the Dakon was in it. Get your shit together, 3rd party publishers.
Like regular Goblins but hairier and and better at climbing. They also tend to knuckle-walk.
From the post-apocalyptic world of the Dark Sun campaign setting, these evil four-armed psychic gorillas have exposed brains. Despite being evil they seem to have a rather loving and egalitarian family life.
Big blue baboons with a spooky howl and lots of speed.
Furry hunched humanoids. They have no language but communicate via hoots and howls.
Four-armed albino gorillas.
Smart four-armed albino gorillas with swords.
"These monsters have the head, body and legs of a gorilla with the sharp teeth and powerful arms of a bear."
Often called "winged deck apes", these simian humanoids are often sailors and pirates.
A D&D monster and a player character race in Pathfinder that can assume Human, monkey, and monkey-faced Human/hybrid forms.
Part of a broad class of Druid-created living weapons, this giant gorilla has red scales, lots of fangs, spikes, horns, and a tail. Their claws also secrete acid. Talk about overkill...
Baboons + wasps = horrifying
These white-furred apefolk have Human faces. Despite personifying "the principles of pacifism and harmony with nature", once every year they go apeshit* and murder a whole bunch of people.
*I had to say it :^)
A creature that's a cross between an ape and a caveman, from the licensed Kingdoms of Kalamar setting for D&D 3.5. They're gender egalitarians! Also, if you kill a Hulking Growler's mate then be prepared for relentless murderous revenge.
A gigantic freaky black-furred baboon with a rat's tail. It can shapeshift into rabbits, puppies, kitties, or other fuzzy wuzzy animals, an ability which it uses to eat children.
There are two types of Kech: One is from D&D and is monkey-like, the other is from Pathfinder and is ape-like. Both have weird leaf-like skin that functions as camouflage. D&D Kechs are predators that stick to jungles; PF Kechs are more likely to stray from their territory. PF Kechs also have a taboo against eating apes and monkeys.
A sapient tauric creature with the upper body of a gorilla and the lower body of a spider. Strangely, the Monster Manual III doesn't mention Driders (evil Elf-Spider creatures) in their description. Drider-Lhosk interactions could prove very interesting indeed.
A beast from the plane of Limbo, it's described as an "anthropomorphic serpent" but is really just a gorilla with some scales and an ugly face.
Like regular Goblins but with more hair and monkey tails. They're also not spineless cowards, unlike their common cousins.
1-inch tall monkeys. They are also sapient, Good-aligned, and their bites are poisonous.
White-furred ape-men that dwell underground. They also hate surface-dwelling Elves for some reason. 3rd edition made them look a little more like bear-people.
These guys are "Yeti-kin". They're rather well-adjusted tribal carnivores who surprisingly don't eat humanoids. They're also immune to cold.
A Pathfinder-only race as far as can tell, these creatures are based on pop culture Bigfoot with some skunk ape and weird hippie vibes thrown in.
Supposedly resembling "thin, gangly apes", these guys look more like really hairy Orcs. They are also mildly psychic and can have ESP. Also, more skin-flaps for gliding.The can also create a friendly psychic ghost-monster called a Revered Ancient One that's an omega-level healbot.
Imagine a shaved gorilla with a lizard face and magic chitin armor. Wizards truly have no sense of right and wrong.
White-furred variants of the average Goblin that dwell in cold areas. Look like ugly tailless monkeys.
Spirit of the Air
Golden monkeys with freaky arm-wings that serve gods of air. They cast spells like Clerics and can transform into a whirlwind once per day.
Big gray psychic monkeys.
Clan-based apefolk similar to cavemen. Dwell in cold mountain regions. Very low tech levels.
A creature that looks like a tusked gorilla head with six arms sprouting from it. It eats Halflings/Hobbits.
One of the "iconic" D&D, it's especially evident in older edition art that Umber Hulks are insectoid apes.
Extroverted monkeyfolk from Oriental Adventures. They get along with every except Evil beings.
Magic robot gorillas.
Not exactly simian, this creature is a fey/fairy equivalent of a werewolf. A terrible flying hunger spirit that flies through the air, instilling madness and paranoia into its prey.
White-furred ape-people of the cold mountains. They are invisible if even lightly covered in snow or ice and their fur drains the heat out of living creatures, making them a weird heat-vampire-ape.