Sauron is known as the first bearer of the One Ring.
Sauron forged the One Ring in the fires of Mount Doom during the Second Age. He created it to dominate the other Rings of Power and extend his control over their bearers. Because much of Sauron’s power was invested in the Ring, its destruction was essential to defeating him permanently.
The Ring was later taken from Sauron by Isildur after Sauron’s defeat at the end of the Second Age. Isildur did not destroy it, and it was eventually lost in the Anduin. Gollum found it centuries later, and Bilbo Baggins took it from Gollum beneath the Misty Mountains.
Those later bearers are often associated most strongly with the Ring, but they were not its first bearer. Sauron’s forging and use of the Ring established its power and purpose.