# List of U-boat types

List of U-boat types contains lists of the German U-boat types (submarine classes) used in World War I and World War II.
The anglicized word U-boat is usually only used as reference for German submarines in the two World Wars and therefore postwar submarine in the Bundesmarine and later German Navy are not included.
In the period between the two World Wars the Reichsmarine of the Weimar Republic was not allowed to build submarines according to the Treaty of Versailles; development was undertaken secretly through a Dutch company NV Ingenieurskantoor voor Scheepsbouw before the mid-1930s. The terms of the Anglo-German naval agreement acknowledged the official building of new U-boats.

## World War I

This list contains the German U-boats types prior or during the First World War.
U-boat types of World War I :
| Type | Year of introduction | Number of U-boats completed |
| U-1 | 1906 | 1 |
| U-2 | 1906 | 1 |
| U-3 | 1907 | 2 |
| U-5 | 1908 | 4 |
| U 9 | 1908 | 4 |
| U 13 | 1909 | 3 |
| U-16 | 1909 | 1 |
| U-17 | 1910 | 2 |
| U-19 | 1910 | 4 |
| U-23 | 1911 | 4 |
| U-27 | 1912 | 4 |
| U 31 | 1912 | 11 |
| U-43 | 1914 | 8 |
| U 51 | 1914 | 6 |
| U 57 | 1914 | 6 |
| U 63 | 1915 | 3 |
| U 66 | 1913 | 5 |
| U 81 | 1915 | 6 |
| U 87 | 1915 | 6 |
| U 93 | 1915 | 22 |
| U 115 | 1916 | 0 |
| U 127 | 1916 | 0 |
| U 139 | 1916 | 3 |
| U 142 | 1916 | 1 |
| U 151 | 1916 | 7 |
| UA | 1912 | 1 |
| UB I | 1914 | 17 |
| UB II | 1915 | 30 |
| UB III | 1916 | 95 |
| UC I | 1914 | 15 |
| UC II | 1915 | 64 |
| UC III | 1916 | 16 |
| UD 1 | 1918 | 0 |
| UE I | 1915 | 10 |
| UE II | 1916 | 9 |
| UF | 1918 | 0 |

## World War II

This list contains the German U-boats types prior or during the Second World War.
U-boat types of World War II :
| Type | Year of introduction | Number of U-boats built | Comments |
| IA | 1934 | 2 | Fleet going ocean boat modeled on World War I designs |
| IIA | 1934 | 6 | Prototype coastal patrol submarine |
| IIB | 1935 | 20 | Improved coastal patrol submarine |
| IIC | 1937 | 8 | Extended range coastal patrol submarine |
| IID | 1939 | 16 | Long range coastal patrol submarine |
| III | | 0 | Design schematics created for a mine-layer submarine. Project was dropped due to design flaws |
| IIIA | | 0 | Prototype small boat carrier designed to hold two fast torpedo boats. Project discontinued due to difficulties launching small boats in heavy seas |
| IV | | 0 | First attempt at a designing a supply U-boat for replenishment at sea. Cancelled shortly after initial designs. |
| V | 1940 | 1 | Prototype boat, known as V-80, to test a chemical reaction engine. |
| VI | | 0 | Prototype steam propulsion submarine |
| VIIA | 1935 | 10 | First practical post-World War I attack submarine |
| VIIB | 1936 | 24 | Standard attack submarine in the early months of World War II |
| VIIC | 1938 | 568 | Attack submarine "work horse" for the majority of World War II. |
| VIIC (Flak) | 1942 | 4 | Special variant of Type VII which removed the deck gun and added extra anti-aircraft guns |
| VIIC/41 | 1941 | 91 | Upgraded attack boat with several additional offensive and defensive features as well as better diving ability. |
| VIIC/42 | 1942 | 0 | Project was cancelled in lieu of contracts for the Type XXI electrical attack boats |
| VIID | 1940 | 6 | Mine layer submarine, few were produced |
| VIIE | | 0 | Early designs indicate this was to be a deep diving submarine |
| VIIF | 1941 | 4 | Designed to be used as torpedo transport. |
| VIII | | 0 | Intended as a fast attack submarine. Never went beyond initial designs |
| IXA | 1936 | 8 | First post World War I long range fleet ocean boat |
| IXB | 1937 | 14 | Standard pre-World War II fleet ocean boat |
| IXC | 1939 | 54 | Upgraded fleet ocean boat used in the opening years of World War II |
| IXC/40 | 1940 | 87 | Enhanced fleet ocean boat with better diving abilities |
| IXD1 | 1940 | 2 | Heavy diesel boat, suffered from numerous design flaws. Rebuilt as long range transports |
| IXD2 | 1940 | 28 | Heavy diesel engine long range fleet boat. Heaviest and largest of the IX series |
| IXD/42 | 1942 | 2 (+ 4 cancelled) | Attempt to upgrade the heavy diesel engine design. Never deployed operationally |
| XA | 1939 | 0 | Designed to be used as mine layer. Retooled as the XB transport boat |
| XB | 1939 | 8 | Long range transport boat |
| XI | 1937 | 0 | "Cruiser submarine" with large deck guns. Project was cancelled |
| XII | | 0 | Initial designs only. Listed as "Advanced Fleet Ocean Boat". Never developed. |
| XIII | | 0 | Initial designs only. Listed as "Advanced Coastal Boat". Never developed. |
| XIV | 1940 | 10 | Designed to be used as supply U-boat. Known by the nickname "Milk Cow" |
| XV | | 0 | Initial designs only. Listed as "Long Range Transport Boat". Never developed. |
| XVI | | 0 | Initial designs only. Listed as "Long Range Repair Boat". Never developed. |
| XVIIA | 1942 | 4 | Fast attack boat with chemical propulsion system |
| XVIIB | 1943 | 3 | Upgraded version of the XVIIB with slightly better abilities |
| XVIIG | 1944 | 0 | Upgraded version of the Type XVII. Boats were ordered but never deployed |
| XVIIK | | 0 | Prototype for a closed cycle diesel engine submarine. Never advanced beyond initial designs |
| XVIII | 1943 | 0 | 2 laid down, not completed. Intended for use as an advanced fast attack boat |
| XIX | | 0 | Initial designs only. Listed as "Long range mine layer". Never developed. |
| XX | | 0 | Prototype for a "Long range transport boat". Project cancelled. |
| XXI | 1943 | 118 | Most advanced U-boat of the Second World War. The first of the "electrical boat" designs |
| XXII | | 0 | Prototype for an "Advanced coastal boat". Project cancelled. |
| XXIII | 1943 | 61 | Late war fast attack submarine, using the electrical boat design |
| XXIV | | 0 | Initial designs only. Listed as "Advanced fleet ocean boat". Never developed. |
| XXV | | 0 | Initial designs only. Listed as "Advanced coastal boat". Never developed |
| XXVI | | 0 | Prototype for a "High speed attack boat". Project cancelled. |
| XXVIIA | 1944 | 53 | Midget submarine "Hecht" |
| XXVIIB | 1944 | 285 | Midget submarine "Seehund" |