Gollum is the creature who says “My Precious” about the Ring in J.R.R. Tolkien’s works.
Gollum was originally a Stoor hobbit named Sméagol. He discovers the Ring in the Gladden Fields and kills his relative Déagol after Déagol refuses to give it to him. The Ring’s influence isolates and transforms Sméagol over many centuries.
He eventually lives beneath the Misty Mountains, where he catches fish and speaks to himself as two competing personalities: Sméagol and Gollum. Bilbo encounters him there during the events of The Hobbit and wins the Ring through a riddle contest.
Gollum is not simply a monster without importance to the plot. His struggle with the Ring affects the quest’s outcome, and his final actions at Mount Doom lead directly to the Ring’s destruction.