Sauron is the creator of the One Ring in J.R.R. Tolkien’s legendarium.
Sauron forged the One Ring in the fires of Mount Doom during the Second Age. He made it to control the other Rings of Power and to extend his influence over their bearers. The Ring contained much of Sauron’s own power, which made it both a source of strength and a vulnerability.
The Elven smith Celebrimbor created the Three Rings independently of Sauron’s direct involvement, while Dwarves and Men received other Rings of Power. Sauron’s design was to dominate these rings through the One, but the Elves perceived his intention and removed their rings before he could control them.
Sauron is not the same character as Morgoth, his former master. Morgoth was the primary dark power of the First Age, whereas Sauron became the central enemy of the Second and Third Ages. The Ring’s destruction in Mount Doom severed Sauron’s ability to regain physical power, though it did not make him an ordinary mortal.