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

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

Sauron created the Ring in the volcanic fire of Orodruin, the mountain known in Sindarin as Amon Amarth. Its power was tied to the fires where it was made, which is why destroying it required taking it back to Mount Doom in Mordor. The Ring was finally destroyed when Gollum fell into the Cracks of Doom while clutching it.

Mount Doom is not simply a generic volcano in the story. It is a central landmark of Mordor and a major symbol of Sauron’s power. Readers sometimes confuse the forging place with the location where Sauron first lost the Ring: the latter was the battlefield near Mount Doom at the end of the Second Age.