Mehregan or Mehregan Feast (in Persian: Jashn-e-Mehregan) is an ancient Iranian autumn festival, observed on the 8th or 9th of October (which corresponds to Mehr day or the 16th of Mehr, the seventh month of the Iranian Calendar), and it is a celebration dedicated in honor of Mithra (Mitra) or Mehr, the Persian god of Light, Love, Knowledge, and Commitment.
It should be also noted that in Pahlavi, Sun means Mehr and Mehregan is the celeberation of the sun and the welcoming of winter ahead. It is also believed that the victory of Fraydoon and Kaveh, the First Iranian Legendary Heroes, over Zahhak (the Persian Mythical Tyrant) happened on Mehr day. According to the legend, on this day several gods and goddesses moved down to the earth and helped Fraydoon to defeat and eventually chain Zahhak within the top of the Mount Damavand.
Mehregan is also a harvest festival often compared to Thanksgiving in North America. In the United States, Thanksgiving is celebrated on the fourth Thursday of November and, in Canada, on the second Monday in October. In fact, in Iranian tradition Mehregan is a celebration of Thanksgiving between family and friends, and charity to the poor. The festival symbolically ends with bonfires and fireworks.
During Pre-Islamic and early Islamic Iran, Mehregan was celebrated with the same magnificence and spectacle as Nowruz. It is believed that Mehregan known as the Mithrakana Festival was an ancient festival even for the Achaemenid kings. And as a tradition, on the day of this great festival, Darius the Great used to identify and to destroy Gaumata (the false king). Mithra, a pre-Zoroastrian guardian angel, was later taken as a Zoroastrian Yazata (in Persian: Mehr-Eezad), and the ancient Indo-Europeans believed Mithra to be the protector of green fields, and at the same time the destroyer of drought and famine. To them Mithra was symbolized by the first rays of sun at dawn. Mithrakana Festival was celebrated by Achaemenian kings as followers of Prophet Zoroaster. Even an unproven theory exists that Achaemenian Nowruz was celebrated on Mithrakana. Later Sassanian kings followed the same tradition with celebrating Mehrega on the month of Mehr and Mehr day.
In ancient Iran, it was customary for people to send or give their king, and each other gifts. It was common for people to give presents that they personally liked. Rich people usually gave gold and silver coins, heroes and warriors gave horses while others gave gifts according to their capacity. Gifts over ten thousand gold coins given to the royal court were registered. At a later time, if the gift-giver needed money, the royal court would then return twice the gift amount to the peoples in need. Kings gave two audiences a year; one audience at Nowruz and other at Mehregan. During the Mehregan celebrations, the king wore a fur robe and gave away all his summer clothes
Many times, even today when a child is born on Mehregan, the parents will name the child with a name combined with Mehr such as Mehri, Mehr-Angeez, Mehraban, Mehraan, Mehr-Taash, Mehr-Dokht, Mehr-Daad, Mehr-Baanu, Mehr-Naaz, Mehr-Noush, Mehr-Yaar, Mehr-Zaad, Bozorg-Mehr, Bozarjo-Mehr, etc.
Today, Mehregan is celebrated by many Iranians. In the Zoroastrian tradition, a special table is laid with the fire vase or an incense burner, a copy of the holy Avesta, a mirror for self-reflection, water as the source of life, various grains for prosperity, fruits and flowers, sweets, wine, coins, and candles. A Zoroastrian religious leader (in Persian: Moabed) recites appropriate prayers, especially Mehr Niyaish, a short prayer in the Avestan language in praise of Mithra. A talk is given to signify the occasion, and food is consumed. A poem is read to glorify the festival and the participants of the party dance to the tune of music until late at night.