Sméagol

From Tolkien Gateway

A Hobbit of Stoor-kind who lived on the banks of the Anduin in the later Third Age. His friend Déagol came upon the One Ring, but Sméagol murdered Déagol and took the Ring. He was eventually exiled by his people, and crept into the roots of the Misty Mountains, where he became the creature of the dark better known as Gollum.