Which Tolkien character says, “My precious”?

The Tolkien character who says “My precious” is Gollum.

Gollum was originally Sméagol, a member of a river-dwelling people related to hobbits. He obtained the One Ring by killing his relative Déagol, then hid beneath the Misty Mountains for centuries while the Ring warped his body and personality.

The phrase “my precious” expresses Gollum’s obsessive attachment to the Ring. Tolkien presents him as both dangerous and pitiable: he commits terrible acts, yet his long enslavement to the Ring makes him part of the tragedy surrounding it. His knowledge of the underground paths helps Frodo and Sam, even as his divided loyalties endanger them.

Gollum first appeared in The Hobbit, where the Ring was not yet fully connected to Sauron’s central weapon. Tolkien later revised that material to fit The Lord of the Rings.