In Tolkien’s legendarium, who created the One Ring?

Sauron created the One Ring in Tolkien’s legendarium.

Sauron forged the Ring in the fires of Mount Doom during the Second Age. He made it as the master ring, intending to control the other Rings of Power and dominate their bearers.

The Ring contains much of Sauron’s own power, which explains both its strength and the danger of destroying it. Its fate is tied to Mount Doom because it can be unmade only in the fire where it was forged.

The Elf-smith Celebrimbor created the other Rings of Power, but Sauron secretly made the One Ring independently. This distinction is a common source of confusion: Celebrimbor made the Elven Rings, while Sauron made the ruling Ring.