Enderman

"This long-limbed, purple-eyed, darker-than-night mob is not one you want to get into a staring contest with. Usually seen in the Nether and The End, its presence is rare in the Overworld. Rarer still - players who've made eye contact with it and then survived to tell the tale. Though I have."

- Tom Stone

Endermen are tall, black neutral mobs from the End that have the ability to teleport.

Spawning
An endermen can spawn at light level 7 or less, on any solid surface having at least three empty spaces above. They can spawn in any dimension.

Java Edition
They spawn commonly in "hauntings" of 4 in the End, or 1-4 in the Overworld where they are rarer than most other mobs. In the Nether they spawn in groups of 4 and are even rarer.

Bedrock Edition
Endermen spawn 1-2 at a time in the Overworld, one at a time in the Nether.

Drops
Endermen drop:
 * 0–1 s. The maximum is increased by 1 per level of Looting, for a maximum of 0-4 with Looting III.
 * 5 experience orbs when killed by a player or a tamed wolf.
 * any block being held (see for more information)

Behavior
"This mob becomes hostile if you attack it (easily avoided) or if you just gaze upon it (oh dear). Considering it can run at you, teleport around the world, and chase you with obsessive persistence just because you looked at it the wrong way, we'll give you some friendly advice: don't get caught staring. You should get that tattooed on the inside of your eyelids to help you remember. Thank us later."

- Tom Stone

Endermen do not attack unless provoked by a player or mob attacking them or looking at their body or head from up to 64 blocks away. When provoked, endermen open their mouths, shake with rage, and frequently make screaming sounds; when provoked by being stared at, they also make a lengthy, loud, threatening sound. If the player maintains eye contact, the enderman does not run, although it may teleport away. Once the player stops looking at the enderman, it runs toward the player to attack. If an aggravated enderman is hit by another player or mob, it ceases attacking its original victim. Endermen even attempt to retaliate against the ender dragon if the dragon hits a group of endermen. An aggravated enderman may also teleport to the location of a player or mob up to 4 chunks away.

They can also step up one full block without having to jump.

Endermen are damaged by melee attacks, water, splash water bottles, and rain, and teleport away when they take damage from any of these ( every half second for water and rain, and for splash water bottles). They repeatedly teleport until they find a dry location. However, endermen do not take damage while standing in a filled cauldron. They also teleport if they take damage from other sources such as suffocation, fire, lava, poison, or the wither effect. Range attacks are generally ineffective against endermen because they simply teleport away before the projectile hits. It is extremely unlikely, but possible, to hit an enderman that happened to teleport himself into the path of a projectile, though.

Endermen pursue the player until they are either killed or become distracted by exterior elements like rain, fire, or sun; they are likely to teleport away to underground locations, such as caves, mineshafts, and strongholds, at daybreak. An enderman (whether neutral or aggravated) in a player's vicinity prevents the player from sleeping on a bed at night, as if any hostile mob were nearby. If the player is already asleep in a bed, it is possible for an enderman to teleport on it and knock the player off, although the player continues sleeping.

Endermen cannot be provoked by players looking at them through transparent blocks or wearing a pumpkin on their head. Endermen cannot normally be provoked while the player is in a boat or minecart, however, they can become aggravated by a player in a minecart from some angles. Attacking an Enderman provokes it even if a pumpkin is worn.

Endermen attempt to kill endermites, provided they were spawned from ender pearls. Endermen can spot endermites from a distance of 64 blocks, similar to being provoked by being stared at.

When under the Invisibility effect, the enderman's eyes are still visible.

Teleportation
When teleporting, for each attempt a random destination is chosen within 32 blocks along each axis (i.e. a 64×64×64 cuboid centered on the current position). It then seeks downwards (regardless of distance, sometimes de-spawning itself) from the chosen destination until the block below is made of a movement-blocking material. The teleportation attempt succeeds if no liquid or solid blocks prevent them from standing at the destination. Thus endermen typically need at least three non-solid blocks above the destination to successfully teleport. An enderman can teleport into waterlogged blocks, however. Exceptions are carpet that is not above a block made of a movement-blocking material and snow layers stacked 10 deep or more, as their materials are not flagged as blocking movement even though the blocks themselves do so.

Endermen always attempt to teleport upon taking damage, such as from water. Most ordinary melee attacks are successful, but are usually followed by an immediate teleport to a few blocks behind the attacking player. When directly attacked by the player, endermen have a chance not to open their mouths. Endermen cannot normally be attacked with projectiles in Java Edition and Legacy Console Edition (including splash potions of harming), as they always teleport away just before being hit. However, they do not teleport if positive potions are thrown at them, including splash potions of regeneration and strength, and do not teleport away from poison potions either. A splash water bottle deals damage to an enderman if it is caught in its radius of effect. If all available blocks within teleport distance are removed or unable to be transported to, it is possible to hit endermen in Java Edition with a projectile, though arrows tend to bounce off dealing no damage on occasion. When teleporting due to damage, an enderman can make up to 64 attempts to teleport.

An enderman cannot teleport while it is in a minecart or boat, although in rain and water it attempts to do so, always teleporting back repeatedly until death. This does not occur in Bedrock Edition.

Endermen do not teleport in the daytime while on soul sand unless they are damaged. They also do not teleport if attacked on their legs or by wolves, as wolves attack at the legs. Endermen also hardly teleport when combating other mobs like iron golems.

Except $$, it is possible for an enderman to teleport at death. An ender pearl drops as soon as the enderman dies, but the experience orbs appear only when the enderman's body disappears. Because of this, it's possible to slay an enderman, pick up the pearl at the point where the enderman received the killing blow, and find the experience at the location to where the enderman teleported. This can occur in all editions of the game.

Moving blocks
Endermen have a unique ability to pick up certain block types and move them around. They pick up blocks in a 4×4×3 region horizontally centered on the enderman and vertically at the same level as the enderman itself. One consequence of this is that an enderman cannot pick up blocks in a completely flat area. Endermen drop the block they are holding on death as an item, though $$ they do not visually let go of the block when dying.

Endermen can pick up the following blocks:

Data packs can change this list by modifying the  block tag.

When carrying a block, the enderman may randomly place it, in a 2×2×2 region horizontally centered on the enderman and vertically at the same level as the enderman itself, if the target location is air with a non-air block beneath and the block is allowed to be placed at the target location.

While endermen may breach walls, bridge fences, break redstone circuitry, and even construct golems by removing or placing blocks, such actions are entirely random and not purposeful.

One can summon an enderman holding any block (including the ones not listed above) using the  NBT data.

For example, to summon an enderman holding with no AI where players are standing:

/summon minecraft:enderman ~ ~ ~ {NoAI:1,carriedBlockState:{Name:"netherrack"}}

Data values
Endermen have entity data associated with them that contain various properties of the mob.

Trivia

 * Notch claimed in public that the enderman is a "subtle reference to "the Slenderman", a similar looking monster with a similar name. Given the later development of the End, it is possible he already had the name in mind, and did not choose it because of the Reddit thread in which their name was revealed. In the Halloween texture pack for Legacy Console Edition, the enderman is re-skinned to look like the Slenderman.
 * The collective noun for a group of endermen is “a haunting of endermen”, as stated by Dinnerbone. Additionally, in the third episode of Minecraft: Story Mode, The Last Place You Look, a player is given the option to correct the grammar of other characters by specifying that the collective noun for a group of endermen is "a haunting of endermen."
 * Switching to spectator mode and taking an enderman’s point of view adds a shader that inverts colors, suggesting that they see the End as an island of blue cobblestone (because end stone is a yellowish version of cobblestone with inverted colors) in a white sky, with white pillars, white endermen with green eyes and a white ender dragon, also with green eyes.
 * The texture for an enderman's eyes is located in a different texture file than the body, allowing their eyes to glow. Because the two textures do not line up perfectly, forcing an enderman to look straight up causes its eyes to turn blank white.
 * The enderman teleportation sound also plays when a player teleports using an ender pearl or chorus fruit.