HNLMS Zeeleeuw (S803) is a Walrus-class submarine of the Royal Netherlands Navy.

[3] Zeeleeuw has been deployed both for naval exercises and in combat operations around the world.

[4] The submarine has undergone a mid-life maintenance and upgrade program between 2014 and 2016, and is currently in active service.

Besides changing the software suite, hardware components were either replaced or upgraded with newer versions.

[11] On 3 December 2015 the Zeeleeuw completed its maintenance and upgrade program and was put back in the water.