The List of U-boat flotillas includes the German U-boat flotillas that served during both World Wars. The bases listed are those where the flotillas spent most of their operational careers. During World War II, submarine flotillas were often deployed for tactical purposes, unlike the surface flotillas of the Kriegsmarine, which were primarily administrative.
This list contains the German U-boats flotillas during the First World War.
This list contains the German U-boats flotillas during the Second World War. After 1941, the U-boat flotillas were in turn organized into U-boat regions.