Hemsö Fortress, Coastal artillery fortress in Härnösand Municipality, Sweden.

Hemsö Fortress is a coastal defence installation at the mouth of the Ångermanälven, centred on the heavy battery at Storråberget built in 1953–1957. Its three twin 15.2 cm gun turrets had a range of over 20 kilometres. The main complex lies 40 metres inside the rock, with lift shafts carrying shells to the guns above; the light battery at Havstoudd housed 112 men.

The decision to build the fortress was taken in 1914, and work began in 1917 but was halted in 1918 and resumed in 1921. It was placed on material readiness in 1925 and completed during World War II. The heavy battery at Storråberget was built between 1953 and 1957, and the last conscripts left in 1989.

The heavy battery at Storråberget was finished in 1957 with three twin 15.2 cm gun turrets whose barrels reached over 20 km. The underground floors, blasted into the rock, held kitchens, mess halls, water and air purification, diesel generators and a sick bay for 320 men, built to keep the garrison self-sufficient for 90 days.

The heavy battery at Storråberget, with its museum opened in summer 2005, sits on Hemsön; the light battery at Havstoudd has housed a conference facility since 2006. The underground main section lies about 40 metres inside the rock, reached by lift shafts built to carry shells up to the guns. Parts of the installations are well preserved and visible.

The heavy battery at Storråberget was designed to withstand a nuclear attack and to keep its 320-man crew self-sufficient for 90 days. Its underground levels held kitchens, mess halls, stores, barracks, water and air purification, diesel generators, a sick bay and fire-control rooms. Elevator shafts carried shells up to the guns on the surface.