What is the name of the ring Bilbo Baggins finds in The Hobbit?

The ring Bilbo Baggins finds in The Hobbit is the One Ring.

Bilbo discovers the ring in the tunnels beneath the Misty Mountains after becoming separated from the dwarf company. It gives its wearer the power of invisibility, although its deeper nature is initially unknown to Bilbo and most of his companions.

The ring was created by Sauron in the Second Age to control the other Rings of Power. Sauron placed much of his own power into it, making the ring central to his strength and to the fate of Middle-earth.

Bilbo initially calls it his “precious” only later in the story’s larger context, while Gollum uses that term much earlier. The One Ring is not one of the three Elven Rings such as Narya or Nenya; those have separate histories and powers.