Asha (; aša) is the Avestan language term (corresponding to Vedic language ṛta) for a concept of cardinal importance to Zoroastrian theology and doctrine. In the moral sphere, aša/arta represents what has been called "the decisive confessional concept of Zoroastrianism." The opposite of Avestan aša is druj, "lie."

Asha is the Zoroastrian concept of "truth, order".