Qūmis (قومس; Arabized form of the Persian word کومش Kōmiš; Ancient Greek: Κωμισηνή Cōmisēnē; Classical Armenian: Կոմշ Komsh), was an important province in pre-Islamic Persia, lying between the southern Alborz chain watershed and the northern fringes of the Dasht-e Kavir desert. In Sassanian period, it was separating the provinces of Ray and Gurgan. Qumis remained a small province of medieval Islamic Persia. Its western boundaries lay in the eastern rural districts of Ray, while in the east it marched with Khurasan. It was bisected by the great Khurasan Road, along which was situated the major cities of (from west to east) Khuwar (Choarene; modern Aradan), Semnan, Shahr-i Qumis (or "Hecatompylos"; the administrative capital; modern Damghan), and Bistam. and in its southeastern extremity was located the town of Biyar (modern Beyarjomand).
The word Qumis started to become obsolete from the beginning of the 11th century. Currently, the region is divided between the modern provinces of Mazandaran and Semnan.
There are remains of several Ismaili castles in the region.