Andraste, according to Dio Cassius, was a Celtic war goddess invoked by Boudica while fighting against the Roman occupation of Britain in AD 61:
I thank thee, Andraste, and call upon thee as woman speaking to woman [...] those over whom I rule are Britons, men that know not how to till the soil or ply a trade, but are thoroughly versed in the art of war and hold all things in common, even children and wives, so that the latter possess the same valour as the men. As the queen, then, of such men and of such women, I supplicate and pray thee for victory, preservation of life, and liberty against men insolent, unjust, insatiable, impious.
She is mentioned only once. She may be the same as Andate, mentioned later by the same source, and described as 'their name for Victory', i.e. the Goddess Victoria. Thayer asserts that she may be related to Andarta also. The goddess Victoria is related to Nike, Bellona, Magna Mater, Cybele, and Vacuna—goddesses who often are depicted on chariots.
Many Neopagan sources describe the hare as sacred to Andraste. This seems to derive from a misreading of the passage in Dio Cassius in which Boudica releases a hare from her gown:
“ "Let us, therefore, go against (the Romans), trusting boldly to good fortune. Let us show them that they are hares and foxes trying to rule over dogs and wolves." When she had finished speaking, she employed a species of divination, letting a hare escape from the fold of her dress; and since it ran on what they considered the auspicious side, the whole multitude shouted with pleasure, and Buduica, raising her hand toward heaven, said: "I thank thee, Andraste, and call upon thee as woman speaking to woman..." ”
The hare's release is described as a technique of divination, with an augury drawn from the direction in which it runs. This appears to be similar to the Roman methods of divination which ascribe meaning to the directions in which birds fly, with the left side being auspicious and the right side inauspicious.
Taking an augury at this point before a battle is thus a means of testing the 'good fortune' of which Boudica speaks, with no implication that the hare is sacred to Andraste. More importantly, the unflattering comparison of the Romans with 'hares and foxes' is not consistent with the reverence one would expect if the hare were a symbol of the Goddess. Boudica is evidently giving thanks to Andraste for the omen of victory and not addressing the hare as Andraste.