Hauptsturmführer was a Nazi Party paramilitary rank that was used in several Nazi organizations such as the SS, NSKK and the NSFK. The rank of Hauptsturmführer was a mid-grade company level officer and was the equivalent of a captain (Hauptmann) in the German Army and also the equivalent of captain in foreign armies. Hauptsturmführer was the most commonly held SS officer rank during the Second World War.