Hellevoetsluis is a small city and municipality in the western Netherlands. It is located in Voorne-Putten, South Holland. The municipality covers an area of 61.20 km² of which 20.10 km² is water and it includes the population centres Nieuw-Helvoet, Nieuwenhoorn, and Oude en Nieuwe Struiten, all former municipalities.
Hellevoetsluis is located on the Haringvliet with the sea, beach, and dunes close by, on the extreme southern edge of the Rijnmond and Europoort areas, close to the broad Zeeland landscape. The name translates as "lock at the foot of the Helle". The Helle was a small local river that disappeared over time.