Agrahayana or Margashirsha,^[1] (Sanskrit: आग्रहायण, romanized: Agrahāyaṇa, Sanskrit: मार्गशीर्ष, romanized: Mārgaśīrṣa, Awadhi: अगहन) is the ninth month of the Hindu calendar. In India's national civil calendar, Agrahayana is also the ninth month of the year, beginning on 16 November and ending on 15 December. Margashirsha means related to the Mrigashīrsha nakṣatra (asterism), which has been known since Vedic times.

In lunar religious calendars, Agrahayana or Margashirsha typically begins either on the new moon or the full moon, depending on the regional tradition, and generally corresponds to the ninth month of the year.

In solar religious calendars, Agrahayana (or Margaḻi in Tamil traditions) begins with the Sun's entry into the zodiac sign Sagittarius (Dhanus Rashi) and is considered the ninth month of the year.

Vaikunta Ekadashi, observed on the Ekadashi (11th lunar day) of Margashirsha month, is celebrated also as Mokshada Ekadashi. Additionally, the 10th Canto, 22nd Chapter of Bhagavata Purana narrates a significant episode where the young, marriageable daughters of the cowherd men of Gokula (gopis) worship goddess Katyayani. During the entire Margashirsha month, considered the first month of the winter season (Śiśira Ritu), the gopis undertook a sacred vow (Vrata) with the desire to have Krishna as their husband.^[2]

Bhairava Ashtami occurs on the Krishna paksha Ashtami of this month of Margashirsha month. According to Hindu tradition, it is believed that on this day, Lord Shiva manifested in his fierce form as Bhairava on Earth. This day is commemorated with special prayers, rituals, and offerings dedicated to Bhairava, who is regarded as the protector and guardian deity.

Margashirsha Guruvar Mahalakshmi Vrat, also known as Margashirsha Devi Vrat, is a sacred observance dedicated to Goddess Lakshmi. This fast is observed on all Thursdays of the Margashirsha month in the Hindu lunar calendar, totaling four days of devotion and prayer. The fast holds special significance, as it is associated with wealth, prosperity, mental and spiritual growth, making it ideal for invoking goddess Lakshmi’s blessings. Devotees recite powerful stotras and hymns, including the Lakshmi Ashtottara Shatanamavali (108 names of Lakshmi), the Śrī Sūkta, and the Mahalakshmi Ashtakam. In Odisha this fast is celebrated as Manabasa Gurubara.

In Tamil Nadu, during this month of Margaḻi, women make kolams or rangoli early in the morning. Devotees usually go to temples each morning and recite Thiruppavai by Andal and Thiruvempavai by Manikkavacakar.^[3]

• Astronomical basis of the Hindu calendar
• Hindu units of measurement
• Hindu astronomy
• Jyotiṣa
• Precession of the earth, Equinox