Main road 21 (Hungary)

The Main road 21 is a south–north direction First class main road in the road in the valley of a Zagyva river, that connects the M3 motorway's Hatvan junction to the, facilitating access from the capital city of Hatvan to Salgótarján-Somoskőújfalu. The road is 65 km long.

The road, as well as all other main roads in Hungary, is managed and maintained by Magyar Közút, state owned company.