List of most successful German U-boats

List of successful U-boats contains lists of the most successful German U-boats in the two World Wars based on total tonnage.

This list contains the 5 most successful German U-boats during the First World War based on total tonnage.

Only sunk commercial vessels are included, not military (warships) nor damaged ships.

This list contains the 10 most successful German U-boats during the Second World War based on total tonnage.

Reason behind her sinking is still unknown with theories ranging from attacks by corvettes HMS Camellia and HMS Arbutus, mines, mechanical failure, and possibly becoming victim of her own torpedoes.