(AD 821–873), Islāmic dynasty of the land of Khorāsān (centred in northeastern Persia), which owed nominal allegiance to the ʿAbbāsid caliph at Baghdad but enjoyed virtual independence. The dynasty was founded by Ṭāhir ibn al-Ḥusayn, a successful military general awarded the eastern lands by the caliph. Ṭāhir's successors pushed their dominion as far as the Indian frontier.