Sauron is the creator of the One Ring in J.R.R. Tolkien’s mythology. He forged it in the fires of Mount Doom during the Second Age to dominate the other Rings of Power and control their bearers.
Sauron was originally a Maia, a powerful spiritual being who served the first Dark Lord, Morgoth. After Morgoth’s defeat, Sauron became the principal enemy of the peoples of Middle-earth and built power through deception, warfare, and the Rings of Power.
The One Ring contains much of Sauron’s own power. As a result, he is greatly weakened when it is separated from him, but he can regain his full strength if it returns to his possession. Its destruction therefore requires the Ring to be taken back to Mount Doom, where it was made.
Morgoth is Sauron’s earlier master, not the maker of the One Ring. Saruman is a later wizard who is corrupted by the desire for power, making all three figures distinct.