What object does Gollum call 'my precious'?

The object Gollum calls “my precious” is the One Ring, the powerful Ring of Power created by Sauron. Gollum’s obsession with it is one of the central tragic threads of The Hobbit and The Lord of the Rings.

Gollum was originally a Stoor Hobbit named Sméagol. He obtained the Ring after murdering his cousin Déagol, who had discovered it while fishing in the River Anduin. The Ring’s influence isolated and corrupted Sméagol, eventually transforming him into the creature called Gollum.

The Ring extended Gollum’s life for centuries, but it also twisted his body and mind. He both loved and hated it, treating it as a possession and almost as part of himself. Bilbo Baggins later found the Ring in Gollum’s underground lair, beginning the chain of events that led to Frodo’s quest.

A common mix-up is the Arkenstone, the jewel sought by Thorin Oakenshield in The Hobbit. Gollum’s “precious” is not that gem, nor a fish or one of the Silmarils. The One Ring is finally destroyed when Gollum falls with it into Mount Doom.