Eregion was an elf homeland first established in SA 750 by the Noldor. It was located in the lands between the Rivers Ganduin and Hoarwell, west of the Misty Mountains and the Moria gate. Its main city was Ost-in-Edhil.

The elves that settled in Eregion, led by Celebrimbor, became good friends with the Dwarves of Moria, and there was much trade and traffic between the two lands. The elves were also great elvensmiths and it is said that the works of Celebrimbor were almost the equal of those of Fëanor.

Unfortunately the elves of Eregion, eager to try and regain some of the splendor that was lost when they left Aman, listened to the advice and lore of Sauron. Sauron was still able to appear fair and had said that he repented his evil deeds of the past.

With Sauron's aid and advice 19 Rings of Power were made in Eregion in the years SA 1500 through SA 1590 - although Sauron had no hand in the making of the last, and greatest, three.

In SA 1693 Sauron began a war with the elves, hoping to take the rings of power for his own use. By SA 1697 Eregion was destroyed, Celebrimbor was killed, the remainder of the elves had left with Elrond and founded the refuge of Imladris, and Sauron had recovered 16 of the rings for his own purposes. Eregion had lasted 947 years as a home for the Noldor.

When the fellowship passed through the region in TA 3019, nothing remained of Eregion save only memories.