HSwMS Sjölejonet (Sle), (Sw. meaning sea lion), was the second ship of the Swedish submarine class Sjöormen, project name A11.

However, the ships where finally completed with for the time extremely large batteries.

[2] The submarine served in the Swedish Navy for almost 30 years and was then sold to Singapore in 1997 together with its four sister ships.

HSwMS Sjöbjörnen was renamed RSS Conqueror after Singapore acquired the boat on 28 May 1999.

She was commissioned into the Republic of Singapore Navy on 26 June 2004 after a major refit.