Aatxe, also known as Etsai or Aatxegorri, is a spirit in Basque Mythology.
Aatxe is described as a shapeshifting spirit capable of assuming many forms, including that of a man, though his favourite is a young red bull. He usually dwells in a cave. At night, in stormy weather, Aatxe will come out and attack criminals and malevolent people whom the laws of man have not yet punished, or, alternately, warn people to stay home when danger is prowling. He is sometimes said to be an emissary of the goddess Mari, who especially punishes those who disrespect her.