The One Ring is the fictional artifact that gives its wearer invisibility in J.R.R. Tolkien’s The Hobbit.
Bilbo Baggins finds the Ring in the caves beneath the Misty Mountains after becoming separated from the Dwarves. Gollum has possessed it for centuries, but Bilbo wins it during the riddle contest and takes it away. The Ring’s invisibility is the first power most readers encounter in The Hobbit.
The Lord of the Rings later reveals that the Ring is far more dangerous: Sauron forged it in the fires of Mount Doom to control the other Rings of Power. Its destruction is necessary to defeat Sauron permanently. The Ring also alters the behavior of those who possess or desire it, making it more than a simple magical disguise.
Bilbo initially calls it his “birthday-present” in the later story, while Gollum calls it his “precious.” Its identity is gradually connected to the larger history of Middle-earth.