What is the title of the leader of the Nazgûl?

The leader of the Nazgûl is the Witch-king of Angmar. He is also called the Lord of the Nazgûl, the Black Captain, and the Pale King. Before becoming a Ringwraith, he was a powerful human king who received one of the Nine Rings from Sauron and was eventually enslaved by its power.

In the Third Age, he established the kingdom of Angmar in northern Middle-earth. From its capital at Carn Dûm, he led campaigns that destroyed the successor kingdoms of Arnor. After Angmar fell, he returned to Mordor and became Sauron’s chief servant among the Nine.

The Witch-king leads the search for the One Ring, stabs Frodo at Weathertop, and commands Sauron’s assault on Minas Tirith. He is finally defeated at the Battle of the Pelennor Fields. Merry’s enchanted Barrow-blade weakens him, allowing Éowyn to deliver the fatal blow. “Mouth of Sauron” is a separate servant and “Khamûl” is another Nazgûl; Gothmog is associated with Sauron’s forces but is not the Ringwraith leader.