Also known as: Smeagol
Originally a Stoor hobbit named Smeagol, he murdered his cousin Deagol to possess the One Ring when Deagol found it in the River Anduin. The Ring granted him unnatural long life but twisted him into a wretched, skulking creature. He retreated beneath the Misty Mountains for nearly five hundred years, talking to himself and the Ring, which he called "my Precious." He lost the Ring to Bilbo in the Riddle-game and spent decades hunting for it, eventually being captured and interrogated by both Sauron and Aragorn.
Gollum is one of Tolkien's most complex characters, a being divided between two personalities: Smeagol, who still retained a capacity for affection and loyalty, and Gollum, the treacherous and Ring-obsessed side. Frodo showed him mercy and pity, and for a time Smeagol served as a guide and seemed to be genuinely reforming. But the influence of the Ring, combined with what he perceived as Frodo's betrayal at Henneth Annun, drove him back to treachery. He led the hobbits to Shelob's lair, intending for the spider to kill them so he could reclaim the Ring. Ultimately, it was Gollum who fulfilled the quest: at the Crack of Doom, he bit the Ring from Frodo's finger and fell into the fire, destroying both himself and the Ring. Gandalf's words proved prophetic: that Gollum had a part yet to play before the end, and that the pity of Bilbo (and Frodo) might rule the fate of many.