One of the five great divisions of Persia, bounded on the east by Afghanistan; on the north by Zakaspie, the transcaspian territory of Russia; and on the south by Kirwan. In ancient times it was the territory immediately east of that ruled by the Sassanids, who occasionally exiled political offenders thither. Thus, in 930 Saadia's friend Josiah the anti-exilarch was banished to Khorasan.

The cities of the province in which Jews are most numerous are Meshed and Herat. In Meshed there is a colony of about 2,000 crypto-Jews, known as "Jadidin," who were nominally converted to Islam early in the nineteenth century under the cruel reign of Shah Nur al-Din's father. Some have migratedto transcaspian territory, and practise Judaism at Merv, Aschabad, Bokhara, and Samarcand.D. E. N. A.