Oberleutnant zur See (OLt zS or OLZS[1] in the German Navy, Oblt.z.S.

in the Kriegsmarine) is traditionally the highest rank of Lieutenant in the German Navy.

Within the navy, officers of this rank were simply addressed as Herr Oberleutnant.

To distinguish naval officers from those of the army, the suffix zur See (at sea) was added in official communications, sometimes shortened to z.S.

In the Volksmarine, the rank was originally used in the same way until the suffix zur See was dropped.