Tahir ibn Muslim was the first Husaynid emir, or sharif, of Medina.
He was the son of Abu Ja'far Muslim, a descendant in the ninth generation of Husayn ibn Ali.
Abu Ja'far had migrated to Egypt from Medina, where the Husaynid line was prominent, and became an important figure at the court of the Ikhshidids and later the Fatimids.
[1] Sometime shortly after his father's death in 976/7, Tahir returned to Medina, where he was quickly recognized by the rest of the Husaynids as their leader.
[2] He remained as ruler of Medina until he died in 992, being succeeded by his son al-Hasan ibn Tahir.