Morgoth is the dark lord defeated at the end of the First Age in J.R.R. Tolkien’s legendarium.
Originally called Melkor, Morgoth was the most powerful of the Ainur who entered Arda. He rebelled against the order established by Eru Ilúvatar and became the primary enemy of the Elves and Men during the First Age. The name Morgoth, meaning “Black Foe of the World,” was given to him by Fëanor.
Morgoth’s wars include the conflicts surrounding the Silmarils, the jewels created by Fëanor. His defeat comes in the War of Wrath, when the Valar and their allies attack him. He is cast out of Arda through the Door of Night.
Sauron is often confused with Morgoth because Sauron later becomes the principal enemy in The Lord of the Rings. However, Sauron originally served Morgoth and rose to power after Morgoth’s defeat. Morgoth therefore belongs chiefly to the mythology of the First Age.