Vedic fire sacrifice (yajna) performed at the junctions of new and full moon fortnights.

Ishti is the Vedic fire sacrifice performed at the junctions of the lunar fortnights — on the day following Amavasya and following Purnima. Together these form the Darsha-Purnamasa, the paired fortnightly offerings prescribed in the Shrauta tradition for every householder who has established the sacred fires. The rite is among the oldest continuously performed Hindu observances, and its structure — invocation of Agni, offering of ghee and grain, and the sharing of the remainder — is the template from which most later domestic pujas descend. Today it is maintained chiefly by families of the Shrauta and Smarta traditions and by Vedic pathshalas. For most households the day is simply marked as an auspicious junction suited to prayer, study and charity.

The yajamana and family fast until the rite is complete, then partake of the consecrated remainder.