The Ring of Thrór was the last of the Seven Dwarven Rings to be recovered by Sauron. It was originally given to Durin III, and it remained in his line for thousands of years until it was inherited by Thrór, the King under the Mountain at Erebor.

Long after Erebor's destruction, Thrór passed the Ring to his son Thráin, who dwelt for many years as an exile from his ancient home. Thráin eventually set out on the Quest of Erebor, but he was captured by the spies of Sauron, and the Ring of Thrór was lost to the enemy.