The was a group of medium-sized coastal submarines built for the Imperial Japanese Navy (IJN) during World War II. The IJN official designation for this class was or . They are also known as Type KS submarine. The type name was shortened to .[1]
In 1940, the IJN designed a point-defence coastal submarine because they wanted to save their larger submarines for fleet battles. The Ro-100 class was derived from the preceding Kaichū type. They displaced 6010NaN0 surfaced and 7820NaN0 submerged. The submarines were 60.9m (199.8feet) long, had a beam of 6m (20feet) and a draft of 3.51m (11.52feet). They had a double hull and a diving depth of 75m (246feet).[2]
For surface running, the boats were powered by two 5000NaN0 diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a 380hp electric motor. They could reach 14.2kn on the surface and underwater. On the surface, the Ro-100s had a range of 3500nmi at ; submerged, they had a range of 60nmi at .[3]
The boats were armed with four internal bow 53.3cm (21inches) torpedo tubes and carried a total of eight torpedoes. They were also armed with two single mounts for 250NaN0 Type 96 anti-aircraft guns or a single 76.2mm L/40 AA gun.[4]
18 boats were built in 1941-1944 under the Maru Rin Programme (Boat #210-218) and the Maru Kyū Programme (Boat #400-408).
| Boat # | Name | Builder | Laid down | Launched | Completed | Results | Fate | |
| 210 | [5] | Kure Naval Arsenal | 1941-06-30 | 1941-06-12 | 1942-08-23 | Sunk by naval mine off Bougainville Island 1943-11-25. | ||
| 211 | Kawasaki-Kōbe Shipyard | 1941-09-30 | 1942-04-17 | 1942-10-31 | Sunk by and PBY southeast of San Cristobal 1943-09-15. | |||
| 212 | Kawasaki-Kōbe Shipyard | 1941-09-30 | 1942-04-17 | 1942-11-17 | Disappeared south of Rabi after 1943-05-09.[6] | |||
| 213 | Kure Naval Arsenal | 1941-06-30 | 1941-12-06 | 1942-10-21 | Sank 1943-06-23 Sank 1943-06-23 | Disappeared in the Solomon Islands after 1943-07-28, possibly sunk by a mine or a PT boat. | ||
| 214 | Kawasaki-Kōbe Shipyard | 1941-11-19 | 1942-07-11 | 1943-02-25 | Sunk by north of the Admiralty Islands 1944-05-23. | |||
| 215 | Kawasaki-Kōbe Shipyard | 1941-11-19 | 1942-07-11 | 1943-03-05 | Sunk by north of the Admiralty Islands 1944-05-31. | |||
| 216 | Kure Naval Arsenal | 1941-12-17 | 1942-05-30 | 1942-12-26 | Sank 1943-07-11 | Sunk by north of the Admiralty Islands 1944-05-22. | ||
| 217 | Kure Naval Arsenal | 1941-12-17 | 1942-05-30 | 1942-12-26 | Sunk by east of Kolombangara 1943-07-21. | |||
| 218 | Kawasaki-Kōbe Shipyard | 1942-04-20 | 1942-10-26 | 1943-04-20 | Sank 1943-10-03 | Sunk by north of the Admiralty Islands 1944-05-26. | ||
| 400 | Kawasaki-Kōbe Shipyard | 1942-04-20 | 1942-10-26 | 1943-04-29 | Sunk by south of Okinawa Island 1945-04-25. | |||
| 401 | Kawasaki-Kōbe Shipyard | 1942-08-20 | 1943-01-26 | 1943-07-06 | Sunk by, and in the Bay of Bengal 1944-02-12. | |||
| 402 | Kawasaki-Kōbe Shipyard | 1942-08-20 | 1943-01-26 | 1943-07-10 | Sank RMS Peshawar 1943-12-23 | Sunk by north of the Admiralty Islands 1944-06-10. | ||
| 403 | Kawasaki-Senshū Shipyard | 1942-06-20 | 1943-03-25 | 1943-09-14 | Sunk by in the Luzon Strait 1945-02-11. | |||
| 404 | Kawasaki-Senshū Shipyard | 1942-07-11 | 1943-04-24 | 1943-10-12 | Sunk by in the Luzon Strait 1945-02-12. | |||
| 405 | Kawasaki-Senshū Shipyard | 1942-10-12 | 1943-06-19 | 1943-11-20 | Sunk by and east of Saipan 1944-06-17. | |||
| 406 | Kawasaki-Senshū Shipyard | 1942-10-12 | 1943-06-19 | 1943-11-30 | Sunk by, and west of Mindoro 1945-02-01. Holmes contradicts the identification,[7] indicating that Ro-115 acknowledged orders to proceed to Manila two days after the supposed date of its sinking, and was more likely to have been sunk by on 1945-02-10.[8] | |||
| 407 | Kawasaki-Senshū Shipyard | 1943-01-16 | 1943-09-13 | 1944-01-21 | Sunk by north of the Admiralty Islands 1944-05-24. | |||
| 408 | Kawasaki-Senshū Shipyard | 1943-01-16 | 1943-09-13 | 1944-01-31 | Sunk by USN patrol bomber southeast of Saipan 1944-05-24. |