In J.R.R. Tolkien’s mythology, where was the One Ring forged?

In J.R.R. Tolkien’s mythology, the One Ring was forged in Mount Doom.

Mount Doom, also called Orodruin, is a volcanic mountain in Mordor. Sauron forged the Ring in its fires during the Second Age, giving the object its power and tying much of Sauron’s strength to it. The mountain’s unique fires are essential to the Ring’s destruction.

At the end of The Lord of the Rings, Frodo travels with the Ring to the Cracks of Doom inside Mount Doom. Frodo claims the Ring rather than willingly destroying it, but Gollum bites off Frodo’s finger, falls into the fire, and carries the Ring with him. Its destruction causes Sauron’s power to collapse.

Mount Doom is distinct from Erebor, the Lonely Mountain, which is central to The Hobbit. It is also not Minas Tirith or Barad-dûr, two other major locations in the story of the War of the Ring.