In the fiction of J.R.R. Tolkien, the Edain were those Men (humans) who made their way into Beleriand in the First Age, and were friendly to the Elves.

The Sindarin word Edain, singular Adan (Quenya Atani, Atan) literally meant Second People, and originally referred to all Men, but later it only applied to the Men of Beleriand and their descendants. The Quenya term Atani kept its old meaning.

They were divided in three large houses, or tribes:

1. The House of Bëor: they were dark-haired and stoutly built, and most resembled the Ñoldor of all Elves. They were first discovered by Finrod Felagund, Lord of Nargothrond, and under his guidance later made their way to the lands of the Ñoldorin lord Amrod, in a place later known as Estolad, the Encampment. They remained loyal to the House of Finarfin, and later settled in the lands of Dorthonion.
2. The Second House, later known as the Haladin or the House of Haleth. They were a reclusive folk, dark-haired but smaller in stature than the Bëorians. They kept separate from the other Men, and later received permission to settle in the forest of Region, part of Doriath. They mostly kept out of the wars.
3. The House of Marach, later best known as the House of Hador. They were tall and golden-haired, and most resembled the Vanyar of all Elves. They were a very numerous and war-like tribe, and the Green Elves of Ossiriand feared them. They later settled in Hithlum by way of Estolad. They were loyal to Fingolfin.

The Bëorians and Marachians shared a common tongue, and were known to each other before settling in Beleriand. The tongue of the Haladin was alien to them.

The House of Bëor was nearly wiped out by Morgoth, and the remainder of its people merged with the Hadorians to become the Númenóreans. It would seem that the Haladin of Beleriand were completely wiped out, or at least disappeared as a separate people.

When the Númenoreans returned to Middle-earth in the Second Age, they encountered many Men who were obviously related to the Atani: they classified these Men as Middle Men, and established friendly relations with them. Examples are the Rohirrim, the Men of Dale, and the Breelanders.

Other Men, such as the Dunlendings, were not recognised as Middle Men because they were related to the Haladin rather than Bëorians or Marachians, and they were hostile to Númenor.

A fourth kind of Men came with the Second House, and called themselves Drûg. This name was adopted in Sindarin as Drúedain: Drûg+Edain. They were a strange people, living with the Haladin in the forest of Brethil, some even apparently made it to Númenor, but they died out or had left before the Akallabêth. In the Third Age, their far kin were known as the Woses of Drúadan Forest.

In Celtic mythology, Edain is an alternate name for Epona.