Den Helder Naval Base (Nieuwe Haven)

Nieuwe Haven is a Royal Netherlands Navy base at Den Helder, in the province of North Holland, on the northern tip of the Dutch mainland at the entrance to the Marsdiep. It is the largest naval base in the Netherlands. The installation is owned by the Ministry of Defence and operated by the Royal Netherlands Navy, and it is closed to the public.

The base is the seat of the Commander of the Royal Netherlands Navy. Since the transfer of the Submarine Service from Rotterdam to Nieuwe Haven, all Dutch naval vessels have Den Helder as their home port, making the base the fleet's sole permanent mooring and support location.

Alongside the quays and mooring facilities, the base includes the Nieuwe Rijkswerf, a naval shipyard used for ship repair and maintenance. The Battery Testing Center (Accu Test Centrum, ATC), established in 1988, tests, charges and discharges batteries, principally the battery installations of the Royal Netherlands Navy's submarines. The Central Sickbay (Centrale Ziekenboeg) is a hospital providing healthcare for navy personnel. A shore power supply built around a 6.6 kV high-voltage cable was installed in 2015 and its capacity enlarged in 2025.

The predecessor establishment at Willemsoord had become too small for large warships before the First World War: its wet dock measured 325 by 135 m with an entrance on the long side, and by the 1920s the 155 m light cruiser Java could not enter it. After the Second World War a government commission examined IJmuiden, Rotterdam, Vlissingen and Den Helder as sites for a new base, and in 1947 Den Helder was selected as the country's principal naval base, with a definitive harbour plan completed in 1948. Construction began in 1949 with the damming of the mouth of the Nieuwediep, the base being laid out on reclaimed land east of that channel. The western part was opened in 1954 by HNLMS Karel Doorman and the remainder of the base was completed in 1958.