Muskö Naval Base is a Swedish underground naval facility on the island of Muskö just south of Stockholm in Haninge Municipality (Haninge Kommun).

You can help expand this article with text translated from the corresponding article in Swedish. (October 2019) Click [show] for important translation instructions. View a machine-translated version of the Swedish article. Machine translation, like DeepL or Google Translate, is a useful starting point for translations, but translators must revise errors as necessary and confirm that the translation is accurate, rather than simply copy-pasting machine-translated text into the English Wikipedia. Consider adding a topic to this template: there are already 301 articles in the main category, and specifying|topic= will aid in categorization. Do not translate text that appears unreliable or low-quality. If possible, verify the text with references provided in the foreign-language article. You must provide copyright attribution in the edit summary accompanying your translation by providing an interlanguage link to the source of your translation. A model attribution edit summary is Content in this edit is translated from the existing Swedish Wikipedia article at [[:sv:Musköbasen]]; see its history for attribution. You should also add the template {{Translated|sv|Musköbasen}} to the talk page. For more guidance, see Wikipedia:Translation.

Quick Facts Type, Site history ...

Muskö naval base
Musköbasen
Muskö in Sweden
HSwMS Sundsvall entering one of the openings to the naval base.
Type	Naval base
Site history
Built	1950–1969
In use	1955–present
Materials	Concrete, stone, steel
Battles/wars	None

Close

The construction of the base started in 1950 and was completed 19 years later in 1969. During the construction about 1.5 million tons of rock were removed. It has 3 docks, originally designed for destroyers and submarines. The underground base itself has an area of several km²^{[citation needed]} and is connected by 20 km (12 mi) of underground roads.

In order to connect the base to the mainland, the Muskö road [sv] was built at the same time as the base. This crosses several bridges and intermediate islands before finally accessing the island of Muskö through the Muskö Tunnel [sv], a 3 km (1.9 mi) long road tunnel running some 70 metres (230 ft) under the sea.^[1]

During the Cold war the underground facility was kept highly secret and not much information about it was known to the public.^[2] In 2004 the Swedish government decided that the navy should be concentrated to two bases only, the Karlskrona Naval Base and the Berga Naval Base, and much of the Muskö base was closed. However some parts of the facility were still used by the military. The underground shipyards were being operated under contract by Kockums AB^[3] and Muskövarvet AB. In the autumn of 2019, as part of an upgrade of defence facilities and manpower, the naval base was revived, and it was announced that it would also serve as seat of the main headquarters of the Swedish Navy.^[4]

One of the Swedish submarine incidents in October, 1982, took place just off Muskö naval base.^[5][6]

A survey carried out in 2000 concluded that sedimentation in the tunnels leading to docks contained PCBs, organotin compounds and heavy metals, mainly mercury and copper.^[7]

In 2019, Swedish naval command in the form of the Naval Staff returned to Muskö.^[8] In early 2020 it was confirmed that the base would be fully reactivated.^[9]