Eriador is a large region in J. R. R. Tolkien's fictional world of Middle-earth. In the Second Age, and possibly much earlier, it was largely forested, but the Dúnedain felled most of the forests to build ships out of them. Much of it was encompassed in the early Third Age by the kingdom of Arnor, which later split into the rival kingdoms of Rhudaur, Arthedain and Cardolan. The Shire occupies part of the former kingdom of Arthedain, while Bree and its neighbouring villages lie on the border with the former Cardolan. The Barrow-wights dwell within ancient burial mounds constructed in the First Age by the Edain as they journeyed to Beleriand. Other important places in Eriador are Rivendell and the abandoned kingdoms of Eregion and Angmar. By the time of the War of the Ring, Eriador was largely deserted.
Its boundaries were:
- To the east, the Misty Mountains.
- To the north, the Ice-bay of Forochel, which flooded part of the lands of Morgoth after the War of Wrath.
- To the west, the mountains of Ered Lindon.
- To the south, the river Greyflood and the land of Enedwaith. After the War of Wrath, part of the southwestern border lies along the shores of Belegaer.
Important rivers were the Lune (Elvish Lhûn), the Brandywine (Elvish Baranduin) and the Greyflood.