Hahnheim lies between Mainz and Worms on the river Selz.

The winegrowing centre belongs to the Verbandsgemeinde Rhein-Selz, whose seat is in Oppenheim.

The council is made up of 17 council members, counting the part-time mayor, with seats apportioned thus: (as at the municipal election held on 9 June 2024) The municipality's arms might be described as thus: Per fess gules and argent, a cock repassant counterchanged.

In the countryside towards Köngernheim on the highway going towards Bundesstraße 420 is an old Jewish graveyard.

In the countryside, especially along the Selz and on the former Alzey–Bodenheim railway right-of-way – the “Amiche” – several biotopes have been established.