How is the one ring finally destroyed?

The One Ring is finally destroyed when Gollum falls with it into the lava of Mount Doom. After biting off Frodo’s finger and reclaiming the Ring, Gollum celebrates wildly, loses his footing, and plunges into the fiery Crack of Doom.

The Ring’s destruction ends Sauron’s power because it was forged by Sauron in Mount Doom and contained a major part of his own power. Once the Ring is destroyed, Sauron’s empire collapses, the Nazgûl perish, and Barad-dûr falls.

A common misunderstanding is that Frodo throws the Ring into the volcano. At the crucial moment, Frodo claims it for himself and refuses to destroy it willingly. Sam also never throws it in. In the novel, Gollum falls accidentally; the film adaptation adds a physical struggle between Frodo and Gollum before the fall.