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 designed it to control the other Rings of Power and to strengthen his dominion over their bearers. Because much of his power was invested in it, destroying the Ring would also destroy his ability to maintain his embodied power.
The Ring was cut from Sauron’s hand by Isildur after the defeat of Sauron at the end of the Second Age. Isildur kept it rather than destroying it, beginning the chain of events that eventually brought it to Frodo Baggins.
Celebrimbor created the Three Elven Rings, while Sauron’s master, Morgoth, was a still earlier and more powerful enemy. Saruman is another servant of evil, but he did not forge the One Ring.