Birthday of Muhammad al-Mahdi (Imam Mahdi) is a public holiday in Iran observed on the 15th day of the Islamic month of Sha'ban.
Mahdi is believed by Shias to be the final Imam of the Twelve Imams.
The Mahdi is the term in Islamic eschatology which refers to the prophesied ultimate savior of humankind.
It will emerge with Isa (Jesus Christ) before the Day of Judgment and will bring peace and justice to the world.
Muhammad al-Mahdi is believed to be this person.
Muhammad al-Mahdi was the son of Hasan al-Askarin, the eleventh Imam of the Twelver Shia Muslims.