Her name literally means 'The Dark One' in Brythonic. She was a war goddess in Celtic Britain. Reportedly, Boudicca, leader of the Iceni tribe who led a rebellion against Roman occupation in AD 61, sacrificed captive Roman women to this goddess, as reported by Dio Cassius in the surviving Excerpta Vaticana fragments of his eighty-volume Histories. She may have been the tutelary deity of the Iceni.

It is further reported that Boudicca released a hare before invoking this goddess and embarking on battle Pagan Celtic Britain. Though it is likely that the release of the hare represents a form of divination (the hare running left being a good omen, and right bad) rather than indicating that the hare was somehow sacred to the goddess.

Andraste is only known from the works of Dio Cassius and may be the same goddess as Andante mentioned later by him. The image shown is derived from a depiction on an Iceni coin and may represent this goddess.

Andraste's name is derived from the reconstructed proto-Celtic elements *an-drixtā- (darkness) along with the feminine ending -a. Thus Andraste may be interpreted as 'The Dark One'. And thus she is probably cognate with the Irish Goddess 'Morrigan'.