What object does Bilbo find in the goblin tunnels?

Bilbo finds the One Ring in the goblin tunnels beneath the Misty Mountains.

During the escape from the goblins in The Hobbit, Bilbo becomes separated from the dwarves and wanders through underground passages. He discovers a small golden ring near an underground lake, where he soon encounters Gollum.

Bilbo and Gollum play a riddle game, with Bilbo’s life at stake. After Bilbo wins, he discovers that the ring makes its wearer invisible. That power allows him to evade Gollum and escape the tunnels, eventually rejoining the dwarves.

Readers sometimes confuse this object with the Arkenstone, which Bilbo later finds inside the Lonely Mountain, or with one of the Elven Rings such as Nenya. In The Hobbit, the ring is initially treated as a useful magic ring; The Lord of the Rings later reveals its full identity as Sauron’s One Ring. Tolkien also revised the riddle-game episode between editions to align it with that larger revelation.