Apaosha (, ) is the Avestan language name of Zoroastrianism's demon of drought. He is the epitomized antithesis of Tishtrya, divinity of the star Sirius and guardian of rainfall. In Zoroastrian tradition, Apaosha appears as Aposh or Apaush.
For many decades, the Avestan common noun apaosha- "drought" was thought to derive from either *apa-uša- "burning away" or *apa-vṛt(a)- "stemming the waters." In the late 1960s, it was proposed that apaoša- was the antonym of an unattested derivative of *pauša- "thriving." This explanation, which is also supported by Old Indicpóṣa with the same meaning, is today well accepted. Avestan apaoša- thus originally meant "not thriving."