Södermanland (SSK)

The Södermanland class is a class of submarines built for the Swedish Navy, derived from the Västergötland class. These submarines were upgraded with a Stirling Air-Independent Propulsion (AIP) system, significantly extending their submerged endurance.

Originally commissioned in 1989 as Västergötland-class vessels, HMS Södermanland and HMS Östergötland underwent a major mid-life reconstruction by Kockums, re-entering service as a new class in 2003 and 2004. Designed to counter Baltic maritime threats, these submarines spent decades conducting covert surveillance, patrol missions, and joint exercises with NATO allies. While HMS Östergötland was decommissioned in 2021, HMS Södermanland received a life-extension refit to remain active until Sweden's next-generation Blekinge-class submarines are deployed. The class's pioneering design also laid the groundwork for Sweden's successful export of refurbished AIP submarines to the Republic of Singapore Navy.