Jász–Nagykun–Szolnok is an administrative county in Hungary. 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 rivers Tisza and Körös flow through the county. The capital of Jász–Nagykun–Szolnok county is Szolnok. Its area is 5582 km2. The county is named after the Ossetians (Jasz) and Cumans (Kun) who settled there, along with Szolnok. The county was part of the Danube–Criș–Mureș–Tisa Euroregion between 1997 and 2004.

Pest is a county (vármegye) in central Hungary. It covers an area of 6,393.14 square kilometres (2,468.41 sq mi), and has a population of 1,339,090 (2023). It surrounds the national capital Budapest and the majority of the county's population live in the suburbs of Budapest. It shares borders with Slovakia and the Hungarian counties Nógrád, Heves, Jász-Nagykun-Szolnok, Bács-Kiskun, Fejér, and Komárom-Esztergom. The River Danube flows through the county. The capital of Pest County is Budapest, although Budapest is not part of Pest County. Starting 2018, they also constitute different NUTS:HU level 2 regions, as previously Pest County has lost catch-up aids from the European Union because of the high development of Budapest.