Heartless

The Heartless are villainous beings composed entirely of darkness, born when a Heart is consumed by it and they are the recurring major antagonists in the Kingdom Hearts video game series. Pureblood Heartless are natural creatures that balance out the Light within the world, however Emblem Heartless are unnatural and throw the worlds into chaos as they actively seek to destroy the Light. There are 397 types of Heartless throughout the video game series.

Origins
The Heartless are born from pure Darkness itself. When a heart is stolen or consumed with hate, the darkness inside it consumes the heart, forming a Heartless. The body and soul then form what is called a Nobody, if the consumed person's will is strong enough. There are two types of Heartless in the series; Pureblood Heartless, which are born directly from hearts, and Emblem Heartless, which are born from a machine that collects darkness and can artificially recreate the heart-stealing process.

Ansem's Studies
Ansem the Wise, ruler of Radiant Garden, studied the Heartless.

Ansem's Reports
The Ansem Reports can be collected by Sora throughout the games. They were written by Ansem and contain information on the Heartless. In Kingdom Hearts II, they also contain information on Organization XIII.

In the manga, Sora once turned into a Heartless until his friends change him back to normal.

Xehanort
Ansem's six apprentices aided in the study of the heart, these being Ienzo, Even, Braig, Dilan, Aeleus, and lastly Xehanort. After Ansem was exiled by Xehanort, Xehanort took his former master's name and lead the other apprentices in deeper studies of the heart. This lead to him corrupting the others and releasing their hearts, thus all the apprentices became separated between their Heartless, and their Nobodies, which formed the group Organization XIII. It was Xehanort who also, while disguised as Ansem and as the Seeker of Darkness, designed the Heartless Machine that manufactured Heartless.

Pureblood Heartless

 * Shadow
 * Gigas Shadow
 * Mega-Shadow
 * Gift Shadow
 * Lion Dancer
 * Candy Apple
 * Poison Apple
 * Flower Rider
 * Rodeo Rider
 * Shadow Witch
 * Shadow Magician
 * Wayward Wardrobe's branchees Heartless
 * Wayward Wardrobe's high-heeled boot Heartless
 * Wayward Wardrobe's skirt Heartless
 * Invisible
 * Orcus
 * Neoshadow
 * Novashadow
 * Shadow Sora
 * Darkball
 * Bit Sniper
 * Gargoyle Knight
 * Gargoyle Warrior
 * Chocolate Gargoyle
 * White Chocolate Statue
 * Massive Possessor
 * Cloudy Sunrise
 * Pink Possessor
 * Shadow Glob
 * Blox Bug
 * Danger Bug
 * Metal Bug
 * Prize Bug
 * Fluttering
 * Flutterings
 * Flame Core
 * Earth Core
 * Water Core
 * Sora's Heartless: Shadow
 * AntiSora
 * Sora's Heartless: Offshoots
 * Sora's Heartless: True Form
 * Darkside
 * Dark Follower
 * Darkside Ω
 * Sora's Heartless: Neo Darkside
 * Possessor
 * Thresholder
 * Shadow Stalker
 * Dark Thorn
 * Possessors
 * Anti-Saïx 
 * Anti-Riku 
 * Dark Hide
 * Darkling
 * Darklings
 * Demon Tower
 * Demon Tide

Emblem Heartless

 * Soldier
 * Stealth Soldier
 * Deserter
 * Sergeant
 * Commander
 * Pumpkin Soldier
 * Diver
 * Air Soldier
 * Large Body
 * Fat Bandit
 * Large Snowman
 * Ringmaster
 * Red Nocturne
 * Blue Rhapsody
 * Yellow Opera
 * Green Requiem
 * Black Ballade
 * Silver Rock
 * Emerald Blues
 * Crimson Jazz
 * Spring Metal
 * Scarlet Tango
 * Grey Caprice
 * Striped Aria
 * Sapphire Elegy
 * Pink Concerto
 * Turquoise March
 * Emerald Serenade
 * Violet Waltz
 * Wicked Watermelon
 * Large Watermelon
 * Huge Watermelon
 * Festive Fireworks
 * Large Fireworks
 * Huge Fireworks
 * Jack O' Lantern
 * Round Rice Cake
 * Large Rice Cake
 * Bitter Macaron
 * Mighty Macaron
 * Swaying Spook
 * Wandering Spook
 * Emerald Sonata
 * Powerwild
 * Bouncywild
 * Sniperwild
 * Wild Shaman
 * Cheery Ape
 * Bandit
 * Red Bandit
 * Swordsman
 * Pot Spider
 * Barrel Spider
 * Pot Scorpion
 * Search Ghost
 * Grand Ghost
 * Hover Ghost
 * Carrier Ghost
 * Living Pod
 * Sheltering Zone
 * Sea Neon
 * Screwdiver
 * Missile Diver
 * Aquatank
 * Jet Balloon
 * Gargoyle
 * Wight Knight
 * Pirate
 * Air Pirate
 * Aerial Viking
 * Battleship
 * Wyvern
 * Tailbunker
 * Avalanche
 * Wavecrest
 * Phantomtail
 * Windstorm
 * Dustflier
 * Defender
 * Eliminator
 * Armed Warrior
 * Wizard
 * High Wizard
 * White Mushroom
 * Black Fungus
 * Rare Truffle
 * Pink Agaricus
 * Gold Tricholoma
 * Angel Star
 * Chimera
 * Creeper Plant
 * Dire Plant
 * Fire Plant
 * Blizzard Plant
 * Poison Plant
 * Dark Plant
 * Creeper Bouquet
 * Prank Bouquet
 * Red Rose
 * White Rose
 * Crescendo
 * Rainy Loudmouth
 * Flare Note
 * Bubble Beat
 * Tornado Step
 * Terrible Tomte
 * Eggster Bunny
 * Warlock Step
 * Trick Ghost
 * Magic Phantom
 * Rabid Dog
 * Snapper Dog
 * Bully Dog
 * Raging Reindeer
 * Rush Sheep
 * Hook Bat
 * Golden Hook Bat
 * Beffudler
 * Bookmaster
 * Runemaster
 * Barrier Master
 * Minute Bomb
 * Skater Bomb
 * Storm Bomb
 * Detonator
 * Sparkler
 * Eggcognito
 * Eggscapade
 * Shenaneggan
 * Huge Shenaneggan
 * Growth Egg
 * Munny Egg
 * Prize Egg
 * Hammer Frame
 * Iron Hammer
 * Silver Hammer Frame
 * Gold Hammer Body
 * Bulky Vendor
 * Rare Vendor
 * Fortuneteller
 * Cannon Gun
 * Camo Cannon
 * Ice Cannon
 * Switch Launcher
 * Jumbo Cannon
 * Rapid Thruster
 * Red Gummi Copter
 * Red Copter Fleet
 * Blue Gummi Copter
 * Blue Copter Fleet
 * Yellow Gummi Copter
 * Yellow Copter Fleet
 * Black Gummi Copter
 * Black Copter Fleet
 * Colorful Copter Fleet
 * Driller Mole
 * Lance Soldier
 * Lance Warrior
 * Morning Star
 * Spiked Crawler
 * Scorching Sphere
 * Gummi Hammer
 * Fiery Globe
 * Icy Cube
 * Snowy Crystal
 * Luna Bandit
 * Graveyard
 * Toy Soldier
 * Aeroplane
 * Gilled Glider
 * Hot Rod
 * Mad Ride
 * Assault Rider
 * Nightwalker
 * Bolt Tower
 * Magnum Loader
 * Strafer
 * Devastator
 * Reckless
 * Living Bone
 * Shaman
 * Necromancer
 * Aerial Knocker
 * Aerial Champ
 * Armored Knight
 * Surveillance Robot
 * Guardian
 * Destroyer
 * Large Armor
 * Clay Armor
 * Solid Armor
 * Land Armor
 * Cymbal Monkey
 * Tricky Monkey
 * Air Battler
 * Aerial Master
 * Artful Flyer
 * Sky Grappler
 * Creepworm
 * Zip Slasher
 * Dual Blade
 * Heat Saber
 * Chill Ripper
 * Blitz Spear
 * Stalwart Blade
 * Dual Durandal
 * Bag O' Jewels
 * Bag O' Coins
 * Bag O' Coal
 * Present Bag
 * Dark Score Bag
 * Nosy Mole
 * Pester Jester
 * Wibble Wobble
 * Strange Tree
 * Circus Clown
 * Armored Archer
 * Poison Archer
 * Paralysis Archer
 * Sleep Archer
 * Chomper Egg
 * Wind-Up Leaf Cake
 * Pretender
 * Great Pretender
 * King Pretender
 * Circus Balloon
 * Bunch O' Balloons
 * Wicked Wick
 * Poison Pot
 * Ratty Rat
 * Ring-A-Ding
 * Piercing Knight
 * Chipper Chef
 * Burrfish
 * Guard Armor
 * Opposite Armor
 * Red Armor
 * Powered Armor
 * Guard Armor Ω
 * Sinister Sweets
 * Spiteful Sweets
 * Trickmaster
 * Crimson Prankster
 * Trickmaster Ω
 * Jack in the Box
 * Egg Master
 * Stealth Sneak
 * Sneak Army
 * Veil Lizard
 * Lurk Lizard
 * Pot Centipede
 * Parasite Cage
 * Behemoth
 * Destroyed Behemoth
 * Arch Behemoth
 * Hocus Pocus
 * Phantom
 * Kurt Zisa
 * Illuminator
 * Prison Keeper
 * Volcanic Lord
 * Blizzard Lord
 * Storm Rider
 * Grim Reaper
 * Groundshaker
 * Mushroom XIII
 * Antlion
 * Infernal Engine
 * Archer (Infernal Engine)
 * Leechgrave
 * Ruler of the Sky
 * Lion Headliner
 * Trident Tail
 * Trident Tail Ω
 * Red Trident Tail
 * Green Trident Tail
 * Blue Trident Tail
 * Submarine Carp
 * Savage Spider
 * Venomous Spider
 * Enraged Arachnid
 * Scourge Spider
 * Malicious Spider
 * Wicked Spider
 * Wretched Witch
 * Gummi Hound
 * Assault Dragon
 * Fortress Crab
 * Fortress Crab Ω
 * Circus Crab
 * Furious Whole Cake
 * Queen Bee
 * Queen Bee Ω
 * Nimble Bee
 * Stinging Bee
 * Jewel Sorceress
 * Jewel Princess
 * Wayward Wardrobe
 * Enraged Elk
 * Cannoned Camel
 * Wily Bandit
 * Closehanded Captain
 * Huge Snowman
 * Ferocious Fins
 * Shipwreck Shark
 * Crown Pretender
 * Ratty Rat Trio
 * Adventurer
 * Werewolf
 * Mean Maiden
 * Mean Maiden's yellow cat Heartless
 * Mean Maiden's purple cat Heartless
 * Martial Monkey
 * Ferry Reaper
 * Iron Giant
 * Metal Giant
 * Heartless Tsum
 * Gear Golem
 * Gearbit
 * Thorned Snake
 * Loudness March

Special Heartless

 * Ansem, Seeker of Darkness
 * World of Chaos

Gummi Heartless

 * Crawler
 * Dragonfly
 * Driller
 * Hunter
 * Hunter-X
 * Pirate Ship
 * Ghost
 * Ghoul
 * Reaper's Wheel
 * Submarine

Other Heartless

 * Clayton - is stated to have "no heart" by Tarzan.
 * Cave of Wonders - is taken control of by Heartless.
 * Oogie's Manor - is controlled by Shadow Globs.
 * Scar - is stated to be a Heartless by Pete.
 * Scar's Ghost - ghost of a Heartless.
 * The Experiment - is said to be an artificial Heartless, and also said to be a Heartless in the Kingdom Hearts Trading Card Game.