The Mahdi (Arabic: ٱلْـمَـهْـدِي‎, meaning "the guided one") is an eschatological redeemer of Islam who, according to some Islamic traditions, will appear and rule before the Day of Judgment and rid the world of evil. In most traditions, the Mahdi will arrive with 'Isa (Jesus) to defeat Al-Masih ad-Dajjal ("the false Messiah", or Antichrist). Although the concept of a Mahdi is not an essential doctrine in Sunni Islam, it is popular among both Sunni and Shia Muslims.

The Mahdi (Arabic: ٱلْـمَـهْـدِي‎, ISO 233: al-mahdī, meaning "the guided one") is an eschatological redeemer of Islam who, according to some Islamic traditions, will appear and rule for five, seven, nine or nineteen years (according to differing interpretations) before the Day of Judgment (yawm al-qiyamah, also known as "the Day of Resurrection") and rid the world of evil.There is no direct reference to the Mahdi in the Quran, only in the hadith (the reports and traditions of Muhammad's teachings collected after his death).