Which Tolkien character discovers the One Ring in The Hobbit?

Bilbo Baggins discovers the One Ring in J.R.R. Tolkien’s The Hobbit.

During his journey beneath the Misty Mountains, Bilbo becomes separated from Thorin’s company and encounters Gollum near an underground lake. While exploring the tunnels, he finds a plain golden ring and keeps it without understanding its true significance.

Bilbo later wins a riddle contest against Gollum and uses the ring’s power of invisibility to escape. In The Hobbit, the object is presented mainly as a useful magical ring; The Lord of the Rings later reveals that it is the One Ring created by Sauron.

Frodo inherits the ring from Bilbo and becomes its principal bearer in the later story. Gollum owned it before Bilbo found it, but he did not discover it in the narrative.