The Södermanland Class consists of the submarines HMS Södermanland and HMS Östergötland. They were originally launched in 1987-1990 as two of the four boats in the Västergötland Class.

The submarines have been modernized at Kockums, including the installation of the Stirling AIP system.

HMS Södermanland was relaunched in 2003 and HMS Östergötland in 2004.

Swedish submarines are designed to operate mainly in colder northern waters. Higher water temperatures can lead to problems with high ambient temperatures and high levels of relative humidity on board.

An important aspect of the Södermanland Class conversion is that the submarines will now be equipped to undertake international peacekeeping missions in warmer and more saline waters. In practice this involves fitting the boats with a completely new refrigeration system employing heat exchangers rather than the direct seawater cooling previously used.

The command and control system of the Södermanland Class submarines is being updated to the latest standards and the boats' stealth properties are being further refined. The submarines are also being equipped with a new air-lock for divers.