Helgoland Habitat, Underwater research station in Altefähr, Germany.

Helgoland Habitat is a former German underwater laboratory, now displayed at the Nautineum Dänholm in Stralsund. It consists of three connected cylindrical chambers: a 2.5 m living area, a 6.5 m instrumentation and engine room, and a 4 m wet laboratory added in 1973, all 2.5 m in diameter and giving 32.5 m² of usable floor space. Overall it measures 14 m long, 7 m wide and 7 m high, and weighs 110 tonnes with ballast.

The station was built by Dräger in Lübeck in 1968 as a cold-water research facility for long-term studies in the Baltic Sea. It allowed scientists to remain on the seafloor for several weeks at a time and carry out continuous observations.

The habitat is named after Helgoland, the island off which it was first deployed in 1969. Since 1998 it has been exhibited at the Nautineum Dänholm in Stralsund, where visitors can see the living area, engine room and the wet laboratory added in 1973.

The habitat is no longer submerged: since 1998 it has been displayed on land at the Nautineum Dänholm in Stralsund, reached by a bridge from the mainland. Visitors view the exterior and the cramped interior sections; the original deployment sites in the North Sea, Baltic Sea and Gulf of Maine are not accessible.

The habitat is no longer underwater: since 1998 it has stood on dry land at the Nautineum Dänholm in Stralsund, an outpost of the German Oceanographic Museum, after being towed there by water from Geesthacht. Visitors can walk around the 14-metre-long, 110-tonne hull.