Agrahāyaṇa or Mārgaśīrṣa,(Hindi: अगहन - agahana; मार्गशीर्ष - Mārgaśirṣa) is a month of the Hindu calendar. In India's national civil calendar, Agrahāyaṇa is the ninth month of the year, beginning on 22 November and ending on 21 December. Since Vedic times, this month is known as Mārgaśīrṣa after the Nakṣatra (asterisms) Mṛgaśiras. In Tamil, the month is known as Maarkazhi.
The word Agrahāyaṇa means the month of Ayana or Equinox (agra=first + ayana = travel of the sun, equinox). The aligning of this name with the Mṛgaśiras Nakṣatra (lambda orionis), gives rise to speculation that this name was given when the sun was near Orion at the time of vernal equinox, i.e. around 7000 years ago.
In lunar religious calendars, Agrahāyaṇa may begin on either the new moon or the full moon around the same time of year, and is usually the 9th month of the year.
In solar religious calendars, Agrahāyaṇa/Maarkazhi begins with the Sun's entry into Sagittarius, and is usually the 9th month of the year.
In the Vaiṣṇava calendar, Keśava governs this month.
Vaikuṇṭha Ekādaśī, the Ekādaśī (i.e. 11th lunar day) of this Mārgaśīṣa month, is celebrated also as Mokṣadā Ekādaśī. The 10th Canto, 22nd Chapter of Bhāgavata Purāṇa, mentions young marriageable daughters (gopis) of the cowherd men of Gokula, worshiping Goddess Kātyāyanī and taking a vrata or vow, during the entire month of Mārgaśīṣa, the first month of the winter season (Śiśira), to get Śrī Kṛṣṇa as their husband.