HSwMS Södermanland (Söd) is a Swedish naval submarine, launched in 1988 and currently in active service.

The submarines in the Västergötland class were able to fire up to six heavy and six light wire-guided torpedoes at the same time against different targets.

Between 2000 and 2004, Södermanland and Östergötland underwent extensive modifications, were extended by 12 metres (39 ft) and fitted with air-independent Stirling engines.

At the same time, the submarines would be modified to handle international missions with operations in hot and salty waters.

[2] During 2022, Södermanland underwent yet another life extension program, in order to be operational until 2028.