A title given to the Dark Lord Sauron, who forged the Ruling Ring in the Fire of Mount Doom. Having tricked the Elves of Eregion into constructing Rings of Power of their own, Sauron poured a great part of his own native strength into his own Ring, creating an artefact of immense power to control the wills of the bearers of other Rings. Sauron ultimately failed in his plan to dominate the Elves, but the Ring that he had made was still surpassingly powerful, and especially strong at bending the wills of Men. With it he created the Nine Ringwraiths that would be his greatest servants through the centuries until the War of the Ring.

Though Sauron was the master Ring-maker, there was one other in Middle-earth who claimed the title. Saruman the Wizard studied the lore of the Rings deeply, and appears to have constructed a lesser Ring of his own, though the nature and powers of Saruman's Ring remain in the realms of mystery.