Arba’een, also known as the Martyrdom of Husayn ibn Ali, is observed primarily in Iran and is celebrated every year forty days after the Day of Ashura, which falls on the 20th or 21st day of the Islamic month of Safar. This significant Shia Muslim religious observance commemorates the martyrdom of Husayn ibn Ali, the grandson of the Prophet Muhammad, who was killed in the Battle of Karbala in 680. The observance culminates a traditional forty-day mourning period that begins on Ashura. During Arba’een, millions of pilgrims travel to the city of Karbala in Iraq to visit the Imam Husayn Shrine, which is both his burial site and a mosque. Although it is primarily a Shia observance, many Sunni Muslims also participate in the pilgrimage. In Iran, Arba’een is recognized as a public holiday, reflecting its importance in Shia Islam.