Kurishk (also Koresck) is a one-horned sheep in Zoroastrian mythology. According to the Bundahishn, there are five species of sheep, the fifth of which is the Kurishk, which is as large as a horse and has a great horn. It lives in the hills. One of Persian kings, Manuschihar, kept a Kurishk as a steed.
Odell Shepard said that the Koresck educated one of the Zend kings, but that is probably a mistranslation of the Bundahishn. It is not even clear if the creature's horn really is singular. Its original prototype is believed to be the mouflon.