​HELLEVOETSLUIS, or Helvoetsluis, a fortified seaport in the province of South Holland, the kingdom of Holland, on the south side of the island of Voorne-and-Putten, on the sea-arm known as the Haringvliet, 51/2 m. S. of Brielle. It has daily steamboat connexion with Rotterdam by the Voornsche canal. Pop. (1900), 4152. Hellevoetsluis is an important naval station, and possesses a naval arsenal, dry and wet docks, wharves and a naval college for engineers. Among the public buildings are the communal chambers, a Reformed church (1661), a Roman Catholic church and a synagogue.