Tahir ibn Husayn (died 822) is a general and governor during the Abbasid caliphate.

Specifically, he serves under al-Ma'mun during the Fourth Fitna and leads the armies that defeat al-Amin, making al-Ma'mun the caliph.

He was born in Phoshang which is a village in the ancient city of Herat (then Khorasan; present day Afghanistan).