Tahir ibn Husayn (Arabic: طاهر بن حسين) (died 822) was a general and governor during the Abbasid caliphate. Specifically, he served under al-Ma'mun during the Fourth Fitna and led the armies that would defeat al-Amin, making al-Ma'mun the caliph. He was born in Phoshang which is a village in ancient city of Herat (then Khorasan present day Afghanistan). Tahir commissioned the Christian theologian, Theodore Abu-Qurrah (died c. 830) to translate the pseudo-Aristotelian De virtutibus animae into Arabic.