It lies in central Hungary and shares borders with the Hungarian counties Pest, Heves, Borsod–Abaúj–Zemplén, Hajdú–Bihar, Békés, Csongrád, and Bács–Kiskun.

The county is named after the Ossetians (Jasz) and Cumans (Kun) who settled there, along with Szolnok.

It consists of the unification of the coat of arms of Jászság, Nagykunság and former Exterior-Szolnok County.

The upper part is divided into two equally spaced vertices from top to bottom.

Rail lines in the county cover 503 km (313 mi) of route.