The Nazgûl (Ringwraiths) are Nine Men who became slaves to the Nine Rings and servants of Sauron, who held the Nine Rings. Sauron gave Men the Nine Rings, and because they desired power they were easily corrupted and turned to evil. In 2250 of the Second Age the Men first appeared in the form that they are known for, as the Nazgûl, the Ringwraiths. They were commanded by Sauron's power using the One Ring. When Sauron was destroyed at Númenor at the end of the Second Age the Nazgûl went into hiding until 1300 of the Third Age, when the Lord of the Nazgûl became the Witch-king of Angmar. In 1640 of the Third Age, the other eight, who had been hiding in the far east, entered Mordor and prepared it for the coming of Sauron, who was hiding in Dol Guldur in the forest of Mirkwood. In 2000 of the Third Age the Nazgûl met with their Lord, and together they stormed Minas Ithil, the Tower of the Moon, and in 2002 they captured it and the palantír that was there. Minas Ithil, which became Minas Morgul, served as the home of the Nazgûl, except for three, who stayed in Dol Guldur until the War of the Ring.

In 3018 of the Third Age Sauron learned that the Ring was in the Shire, so he sent forth his Nazgûl to find a hobbit named Baggins. They found what they sought upon Weathertop, and Frodo was wounded by Morgul Knife. He was poisoned, but saved from death by his yellilng of the Elvish phrase, A! Elbereth gilthoniel! The horses of the Nazgûl were later destroyed by the flood at the Ford of Bruinen. The Nazgûl returned the next year on winged beasts. All the Nazgûl were slain at the destruction of the Ring, save their Captain. The Lord of the Nazgûl was slain in the Battle of the Pelennor fields by Éowyn, with assistance from Meriadoc the hobbit.

Sauron used the Nazgûl for they were swift and could outride almost any steed. They were also used to lead armies, for they could freeze enemies with their voices or their presence alone. Nazgûl could only be harmed by enchanted blades, and any weapon which touched them melted. The Nazgûl had the greatest strength at night and in unpeopled places. They had a terrible fear of fire, and were even more terrified of the name of Elbereth. The Nazgûl could only be seen in true form, as kings of old, by those who could witness things in the Wraith World, a grey hazy world. Otherwise, they could only be spotted by their black cloaks. They could not see in the sense that we do, for they could see only in the Wraith World, but they had a keen sense of smell. They could release terrible, ear-piercing, high pitched cries to frighten their enemies, and they used the Black Speech of Mordor.

The identity of only one of the Nazgûl is known. The second highest in command was called, during his earthly life, Gothmog. As a Ringwraith he was called Khamûl.