Vattenborgen, Water tower in Karlskrona, Sweden

Vattenborgen is a neo-Romantic building in Norman castle style on the south side of Stortorget in Karlskrona, between Fredrikskyrkan and Trefaldighetskyrkan. Built 1861–1863 as a water reservoir, it has a crenellated wall and loopholes and covers a cistern of about 1,100 m².

Karlskrona faced serious water problems in the early 1800s because the wells on the island of Trossö could not supply enough water for the growing population. After a severe cholera outbreak in 1853, the city finally decided to build a modern water pipeline system and construct Vattenborgen as a storage reservoir.

The building's Norman-style castle look, with crenellations and loopholes, was chosen for a water reservoir completed in 1861–1863. From the 1960s it housed a restaurant called Restaurang Kaskad, later a hot dog stand and pizzeria. Between 6 June 2009 and 21 January 2018 the Kulenovic Collection of art was shown inside.

Vattenborgen stands on the south side of Stortorget, between Fredrikskyrkan and Trefaldighetskyrkan, on the island of Trossö. The building can be seen from the square; its interior is not open as a regular sight. It is part of the Karlskrona World Heritage Site inscribed in 1998, so it fits into a walk across the square.

The Kulenovic Collection, an art collection, was housed in Vattenborgen from 6 June 2009 to 21 January 2018. Since 2018 the building has been owned by the company Stenhusen Vattenborgen AB. In July 2020 a restaurant and nightclub opened there, but it went bankrupt the following year.