The submarines were medium-sized submarines of the Imperial Japanese Navy (IJN), serving during the 1920s and World War II. The Type L submarines were built with Vickers naval technical guidance. All boats were built in the Mitsubishi Heavy Industries-Kobe Shipyard by the contract with Vickers.
The Type L submarines were divided into four classes:
In 1916, the Mitsubishi Shipbuilding Corporation got the Vickers L class submarine informations. Mitsubishi which lost competition to the Kawasaki's Type F submarines (Fiat-Laurenti design, Ro-1 class and Ro-3 class), bought the license for the L class submarine from Vickers. The IJN hoped an improvement of submarine technologies will be achieved and ordered this submarine from Mitsubishi. Mitsubishi bought six submarine kits, and built two boats by semi-knock down. The submarine crews were satisfied with the Vickers diesels because they proved to be reliable. The IJN studied the diesel engines and made many variants of similar design, for example: Kampon Mk.24 diesel for the Ro-100 class.
| Boat | Laid down | Launched | Completed | Note, fate |
| [1] ex-Submarine No. 25 | 10-08-1918 | 10-10-1919 | 30-06-1920 | Renamed Ro-51 01-11-1924. Decommissioned 01-04-1940. |
ex-Submarine No. 26 | 10-08-1918 | 09-03-1920 | 30-11-1920 | Renamed Ro-52 01-11-1924. Decommissioned 01-04-1932. |
The Type L2 had minor changes from the Type L1. The changes were:
| Boat | Laid down | Launched | Completed | Note, fate |
ex-Submarine No. 27 | 01-04-1919 | 06-07-1919 | 10-03-1921 | Renamed Ro-53 01-11-1924. Decommissioned 01-04-1940. |
ex-Submarine No. 28 | 01-11-1919 | 13-11-1920 | 10-09-1921 | Renamed Ro-54 01-11-1924. Decommissioned 01-04-1940. |
ex-Submarine No. 29 | 30-03-1920 | 10-02-1921 | 15-11-1921 | Renamed Ro-55 01-11-1924. Decommissioned 01-04-1940. |
ex-Submarine No. 30 | 10-07-1920 | 11-05-1921 | 16-01-1922 | Renamed Ro-56 01-11-1924. Decommissioned 01-04-1940. |
The Type L3 is a license production model of the British L class submarine Group 2.
| Boat | Laid down | Launched | Completed | Results | Note, fate |
ex-Submarine No. 46 | 20-11-1920 | 03-12-1921 | 30-07-1922 | Renamed Ro-57 01-11-1924. Decommissioned 20-11-1945. Later scuttled off Kure. | |
ex-Submarine No. 47 | 15-02-1921 | 02-03-1922 | 25-11-1922 | Renamed Ro-58 01-11-1924. Decommissioned 15-09-1945. Later scuttled off Shimizu. | |
ex-Submarine No. 57 | 18-05-1921 | 28-06-1922 | 20-03-1923 | Renamed Ro-59 01-11-1924. Decommissioned 20-11-1945. Scuttled at Iyo-nada, May 1946. | |
The Type L4 is a license production model of the British L class submarine Group 3. Their performance was good. The IJN was satisfied with them and stopped the development of Kaichū type submarines for a long time. Later the IJN was not able to regain the technical delay in development of the medium-sized submarines until the end of the Pacific War.
| Boat | Laid down | Launched | Completed | Results | Note, fate |
ex-Submarine No. 59 | 05-12-1921 | 20-12-1922 | 17-09-1923 | Renamed Ro-60 01-11-1924. Lost in an accident at Kwajalein 29-12-1941. | |
ex-Submarine No. 72 | 05-06-1922 | 19-05-1923 | 09-02-1924 | Damaged 30-08-1942 | Renamed Ro-61 01-11-1924. Sunk by 31-08-1942. |
ex-Submarine No. 73 | 08-09-1922 | 29-09-1923 | 24-07-1924 | Renamed Ro-62 01-11-1924. Decommissioned 20-11-1945. Scuttled at Iyo-nada, May 1946. | |
ex-Submarine No. 84 | 02-04-1923 | 24-01-1924 | 20-12-1924 | Renamed Ro-63 01-11-1924. Decommissioned 20-11-1945. Scuttled at Iyo-nada, May 1946. | |
ex-Submarine No. 79 | 15-10-1923 | 19-08-1924 | 30-04-1925 | Renamed Ro-64 01-11-1924. Sunk by naval mine at Hiroshima Bay 12-04-1945. | |
| 15-11-1924 | 19-09-1925 | 30-06-1926 | Lost in an accident at Kiska 04-11-1942. | ||
| 01-12-1925 | 25-10-1926 | 28-07-1927 | Collided with Ro-62 and sunk southwest of Wake Island 17-12-1941. | ||
| 05-03-1925 | 18-03-1926 | 15-12-1926 | Decommissioned 20-07-1945. Scuttled off Sasebo, July 1948. | ||
| 06-02-1924 | 23-02-1925 | 29-10-1925 | Decommissioned 30-11-1945. Scuttled off Maizuru, 30-04-1946. | ||
| Type | L1 (Ro-51) | L2 (Ro-53) | L3 (Ro-57) | L4 (Ro-60) | |
| Displacement | Surfaced | 893LT | 893LT | 889LT | 988LT |
| Submerged | 1075.2LT | 1075.3LT | 1102.7LT | 1301LT | |
| Length (overall) | 70.59m (231.59feet) | 70.59m (231.59feet) | 72.89m (239.14feet) | 78.39m (257.19feet) | |
| Beam | 7.16m (23.49feet) | 7.16m (23.49feet) | 7.16m (23.49feet) | 7.41m (24.31feet) | |
| Draft | 3.9m (12.8feet) | 3.94m (12.93feet) | 3.96m (12.99feet) | 3.96m (12.99feet) | |
| Power plant and shaft | 2 × Vickers diesels, 2 shafts | 2 × Vickers diesels, 2 shafts | 2 × Vickers diesels, 2 shafts | 2 × Vickers diesels, 2 shafts | |
| Power | Surfaced | 2,400 bhp | 2,400 bhp | 2,400 bhp | 2,400 bhp |
| Submerged | 1,600 shp | 1,600 shp | 1,600 shp | 1,600 shp | |
| Speed | Surfaced | 17kn | 17.3kn | 17.1kn | 15.7kn |
| Submerged | 10.2kn | 10.4kn | 9.1kn | 8.6kn | |
| Range | Surfaced | 5500abbr=onNaNabbr=on at 10kn | 5500abbr=onNaNabbr=on at 10kn | 5500abbr=onNaNabbr=on at 10kn | 5500abbr=onNaNabbr=on at 10kn |
| Submerged | 80abbr=onNaNabbr=on at 4kn | 80abbr=onNaNabbr=on at 4kn | 80abbr=onNaNabbr=on at 4kn | 80abbr=onNaNabbr=on at 4kn | |
| Test depth | 60m (200feet) | 60m (200feet) | 60m (200feet) | 60m (200feet) | |
| Fuel | 75 tons | 75 tons | 75 tons | 75 tons | |
| Complement | 45 | 45 | 46 | 48 | |
| Armament (initial) | • 6 × 4500NaN0 TTs (4 × bow, 2 × broadside) • 10 × Type 44 torpedoes • 1 × 76.2mm L/23.5 AA gun | • 4 × 450 mm TTs (4 × bow) • 8 × Type 44 torpedoes • 1 × 76.2 mm L/23.5 AA gun | • 4 × 5330NaN0 TTs (4 × bow) • 8 × 6th Year Type torpedoes • 1 × 76.2 mm L/23.5 AA gun • 1 × 6.5 mm machine gun | • 6 × 533 mm TTs (6 × bow) • 12 × 6th Year Type torpedoes • 1 × 76.2mm L/40 naval gun • 1 × 6.5 mm machine gun | |