Preparatory Vedic rite performed the day before a major fire sacrifice or yajna.

Anvadhan is the preparatory day that immediately precedes Ishti. On this day the sacred fires are ritually replenished — fresh fuel is added, the fire is re-established and consecrated, and the materials for the following day sacrifice are gathered and purified. The word itself means the additional placing, referring to the fresh samidha laid on the fire. In the Shrauta scheme, Anvadhan and Ishti are inseparable: the first prepares, the second offers. It falls on Amavasya and on Purnima, the two days on which the moon reaches its extremes, with the Ishti following on the next day. For households not maintaining the sacred fires, the day is observed simply as one of preparation, cleaning and purification before an auspicious junction.

No formal fast is prescribed. A single simple satvik meal is customary, taken after the evening offering, in preparation for the Ishti.