Type 81 was a class of U-boats built during World War I by the Kaiserliche Marine.

They carried a crew of four officers and 31 men and had excellent seagoing abilities with a cruising range of around 11,220 nautical miles (20,780 km; 12,910 mi).

[citation needed] Compared to the previous type 63, the 81s were 1.7 metres (5 ft 7 in) longer, while the pressure hull remained the same.

[citation needed] Compared to the following type 87, the 81s were 4.26 metres (14.0 ft) longer, yet 5 tons lighter.

[citation needed] Type 81 boats were responsible for sinking 3.537% of all Allied shipping sunk during the war, accounting for a total of 427,247 combined tons.