A period of a thousand years foretold in the Book of Revelation. During the millennium, those who have been faithful to Jesus and who have not worshiped the Antichrist will reign with Jesus over the Earth. According to the Book of Revelation, the millennium will precede the final battle for control of the universe; Judgment Day will come afterward.
Note: The meaning of the Bible's words about the millennium has been much debated by Christians. Prophecies about the millennium are part of the basic doctrine of several denominations, including Jehovah's Witnesses.
Note: Figuratively, a “millennium” is a period of great justice and happiness on Earth.