The 7.5 cm PaK 40 (7.5 cm Panzerabwehrkanone 40) was a German 7.5 centimetre anti-tank gun developed in 1939-1941 by Rheinmetall and used during the Second World War. PaK 40 formed the backbone of german anti-tank guns for the latter part of World War II, and was used in most war theatres.