Imperial Japanese Navy ship classifications went through various changes between 1871 and 1945, as technology changed and new ship classes were added while those that became obsolete were discontinued. There were efforts to translate some ships' classes that were imported or in use by other navies, while incorporating any classification system into Japanese language conventions and maintaining an internal consistency.

Classification terminology

These were legal classifications of the naval vessels of the Imperial Japanese Navy. Therefore, those names are different from universal classifications and class names.

In laws, ordinances, regulations, and policies pertaining to the Imperial Japanese Navy, there were no classifications related to the light aircraft carrier, escort carrier, heavy cruiser or light cruiser. Even if it is assumed that these translation were different in the Japanese language, there could be the same phrase and class in English language, and vice versa.

• Example 1: Kōsakukan (工作艦) and Kōsakusen (工作船) = Repair ship.
• Example 2: Fusetukan (敷設艦), Fusetsusen (敷設船), and Fusetsutei (敷設艇) = Minelayer.

The suffix of ship classes could also relate the type or structure of the vessel, which may carry a slightly different connotation than the translated English term. SOme examples:

• -kan (艦) = Vessel or Ship, example: Kōsakukan is Repair vessel; Senkan is a Battleship.
• -sen (船) = Ship, example: Kōsakusen is Repair ship.
• -tei (艇) = Boat, example: Fusetsutei is Mine boat.

Representative classification tables

Detailed classification tables

Battleship

1st class battleship Yashima

Battleship Yamato

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Warships		Battleship	1st class battleship	And over 10,000 tons designated displacement
				2nd class battleship	Less than 10,000 tons designated displacement
22 June 1900	Naval Vessels	Warships	Battleship	1st class battleship	Same as on 21 March 1898
				2nd class battleship
12 December 1905	Naval vessels	Warships	Battleship		'Class' was abolished

Battlecruiser

Battlecruiser Ibuki

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
28 August 1912	Naval Vessels	Warships	Battlecruiser
30 May 1931					Abolished and unified to battleship

Cruiser

1st class cruiser Nachi

3rd class cruiser Suma

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Warships		Cruiser	1st class cruiser	And over 7,000 tons designated displacement
				2nd class cruiser	And over 3,500 tons designated displacement, less than 7,000 tons designated displacement
				3rd class cruiser	Less than 3,500 tons designated displacement
22 June 1900	Naval Vessels	Warships	Cruiser	1st class cruiser	Same as on 21 March 1898
				2nd class cruiser
				3rd class cruiser
28 August 1912	Naval vessels	Warships	Cruiser	1st class cruiser	And over 7,000 tons designated displacement
				2nd class cruiser	Less than 7,000 tons designated displacement, '3rd class' was abolished.
31 May 1934	Naval vessels	Warships	Cruiser	1st class cruiser	Equipped over 155 mm (6.1 in) gun
				2nd class cruiser	Equipped and under 155 mm (6.1 in) gun

Aircraft carrier

Aircraft carrier Akagi

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
1 April 1920	Naval Vessels	Warships	Aircraft carrier

Seaplane tender

Seaplane tender Chitose

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
31 May 1934	Naval Vessels	Warships	Seaplane tender		Independent from aircraft carrier

Dispatch vessel

Dispatch vessel Miyako

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Warships		Dispatch vessel		Torpedo gunboat was classified to dispatch boat
22 June 1900	Naval vessels	Warships	Dispatch vessel
28 August 1912					Abolished and unified to gunboat

Torpedo boat tender/Submarine tender

Torpedo boat tender Toyohashi

Submarine tender Tsurugizaki

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Warships		Torpedo boat tender
22 June 1900	Naval vessels	Warships	Torpedo boat tender
28 August 1912					Abolished and unified to coast defence ship
1 April 1920	Naval vessels	Warships	Torpedo boat tender		Revived
1 December 1924	Naval vessels	Warships	Submarine tender		Renamed

Minelaying ship/Minelayer/Rapid extension netlayer

Minelayer Tsugaru

• Note; pertinence of rapid extension netlayer was only Shirataka.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
17 May 1916	Auxiliary ships		Minelaying ship
1 April 1920	Naval vessels	Warships	Minelayer		Renamed
2 March 1927	Naval vessels	Warships	Minelayer
			Rapid extension netlayer
22 March 1929	Naval vessels	Warships	Minelayer		Rapid extension netlayer was abolished, and unified to minelayer

Training battleship

Training battleship Hiei

• Note; pertinence of training battleship was only Hiei. She does not return to battleship in the Imperial Japanese Navy's official documents.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
30 May 1931	Naval vessels	Warships	Training battleship

Training cruiser

Training cruiser Katori

• Note; pertinence of training cruiser was only Katori class.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
30 May 1931	Naval vessels	Warships	Training cruiser

Coast defence ship

2nd class coast defence ship Itsukushima

Coast defence ship Shisaka

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Warships		Coast defence ship	1st class coast defence ship	And over 7,000 tons designated displacement
				2nd class coast defence ship	And over 3,500 tons designated displacement, less than 7,000 tons designated displacement
				3rd class coast defence ship	Less than 3,500 tons displacement
22 June 1900	Naval vessels	Warships	Coast defence ship	1st class coast defence ship	Same as on 21 March 1898
				2nd class coast defence ship
				3rd class coast defence ship
28 August 1912	Naval vessels	Warships	Coast defence ship	1st class coast defence ship	And over 7,000 tons designated displacement
				2nd class coast defence ship	Less than 7,000 tons designated displacement
30 May 1931	Naval vessels	Warships	Coast defence ship		'Class' was abolished
1 July 1942	Naval vessels		Coast defence ship (as Escort ship)		Armored cruisers were moved to 1st class cruiser or auxiliary training ship

Gunboat

1st class gunboat Saga

Gunboat Sumida

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Warships		Gunboat	1st class gunboat	And over 1,000 tons designated displacement
				2nd class gunboat	Less than 1,000 tons designated displacement
22 June 1900	Naval vessels	Warships	Gunboat	1st class gunboat	Same as on 21 March 1898
				2nd class gunboat
28 August 1912	Naval vessels	Warships	Gunboat	1st class gunboat	And over 800 tons displacement
				2nd class gunboat	Less than 800 tons displacement
30 May 1931	Naval vessels	Warships	Gunboat		'Class' was abolished
1 October 1944	Naval vessels		Gunboat

Torpedo boat destroyer/Destroyer

1st class destroyer Shimakaze

3rd class destroyer Kagerō

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
21 March 1898	Torpedo boat		Torpedo boat destroyer
22 June 1900	Naval vessels	Warships	Destroyer		Independent from torpedo boat and renamed
12 December 1905	Naval vessels		Destroyer
28 August 1912	Naval vessels		Destroyer	1st class destroyer	And over 1,000 tons designated displacement
				2nd class destroyer	And over 600 tons designated displacement, less than 1,000 tons designated displacement
				3rd class destroyer	Less than 600 tons designated displacement
30 May 1931	Naval vessels		Destroyer	1st class destroyer	And over 1,000 tons designated displacement
				2nd class destroyer	Less than 1,000 tons designated displacement, '3rd class' was abolished
31 May 1934	Naval vessels		Destroyer	1st class destroyer	And over 1,000 tons standard displacement
				2nd class destroyer	Less than 1,000 tons standard displacement

Submersible/Submarine

No. 1-class submersible

1st class submarine I-400

• Note; Kō-hyōteki, Kairyū and Kaiten were not included in this table, because they were weapons in the Imperial Japanese Navy's official documents.^[1]

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
23 January 1905	Torpedo boat		Submersible
12 December 1905	Naval vessels		Submersible		Independent from torpedo boat
28 August 1912	Naval vessels		Submersible	1st class submersible	And over 600 tons surfaced displacement
				2nd class submersible	Less than 600 tons surfaced displacement
4 April 1919	Naval vessels		Submarine	1st class submarine	Renamed; and over 1,000 tons surfaced displacement
				2nd class submarine	Renamed, and over 600 tons surfaced displacement, less than 1,000 tons surfaced displacement
				3rd class submarine	Less than 600 tons surfaced displacement
30 May 1931	Naval vessels		Submarine	1st class submarine	And over 1,000 tons surfaced displacement
				2nd class submarine	Less than 1,000 tons surfaced displacement, '3rd class' was abolished

Torpedo boat

1st class torpedo boat Hayabusa

2nd class torpedo boat No. 21

3rd class torpedo boat No. 14

Torpedo boat Kiji

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
13 August 1890	Naval ships	Category 'B' warship	Torpedo boat
19 October 1893	Naval ships	Category 'B' warship	Torpedo boat	1st class torpedo boat	And over 70 tons displacement
				2nd class torpedo boat	And over 20 tons designated displacement, less than 70 tons designated displacement
				3rd class torpedo boat	Less than 20 tons designated displacement (vedette boat)
28 March 1896	Naval ships		Torpedo boat	1st class torpedo boat	Same as on 19 October 1893
				2nd class torpedo boat
				3rd class torpedo boat
21 March 1898			Torpedo boat	Torpedo boat destroyer
				1st class torpedo boat	And over 120 tons designated displacement
				2nd class torpedo boat	And over 70 tons designated displacement, less than 120 tons designated displacement
				3rd class torpedo boat	And over 20 tons designated displacement, less than 70 tons designated displacement
				4th class torpedo boat	Less than 20 tons designated displacement (vedette boat)
22 June 1900	Naval vessels		Torpedo boat	1st class torpedo boat	Same as on 21 March 1898; Torpedo boat destroyer was independent from torpedo boat, and renamed destroyer.
				2nd class torpedo boat
				3rd class torpedo boat
				4th class torpedo boat
23 January 1905	Naval vessels		Torpedo boat	1st class torpedo boat	Same as on 21 March 1898
				2nd class torpedo boat
				3rd class torpedo boat
				4th class torpedo boat
				Submersible	IJN called Special-Torpedo boat (特号水雷艇, Tokugō-Suiraitei) for counterintelligence
12 December 1905	Naval vessels		Torpedo boat	1st class torpedo boat	Same as on 21 March 1898 Submersible was independent from torpedo boat.
				2nd class torpedo boat
				3rd class torpedo boat
				4th class torpedo boat
28 August 1912	Naval vessels		Torpedo boat	1st class torpedo boat	And over 120 tons designated displacement
				2nd class torpedo boat	Less than 120 tons designated displacement
15 January 1924					Abolished
30 May 1931	Naval vessels		Torpedo boat		Revived by the London Naval Treaty

Mine boat/Capture-net layer

2nd class mine boat Tsubame

Mine boat Kamishima

• Note; pertinence of capture net layer was only Tsubame class.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
1 July 1920	Auxiliary vessels	Auxiliary boat	Mine boat	1st class mine boat	And over 800 tons displacement
				2nd class mine boat	And over 400 tons designated displacement, less than 800 tons designated displacement
				3rd class mine boat	Less than 400 tons designated displacement
2 March 1927	Auxiliary vessels	Auxiliary boat	Mine boat	1st class mine boat	Same as on 1 July 1920
				2nd class mine boat
				3rd class mine boat
			Capture-net layer
22 March 1929	Auxiliary vessels	Auxiliary boat	Mine boat	1st class mine boat	Same as on 1 July 1920; capture-net layer was abolished and unified to mine boat
				2nd class mine boat
				3rd class mine boat
30 May 1931	Auxiliary vessels	Auxiliary boat	Mine boat		'Class' was abolished
1 February 1944	Naval vessels		Mine boat

Auxiliary minelayer

Auxiliary minelayer No. 1

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
1 February 1944	Auxiliary vessels	Auxiliary boat	Auxiliary minelayer		Divided from mine boat

Cable layer

Cable layer Hashima

• Note; pertinence of cable layer was only Hashima class.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
25 October 1940	Auxiliary vessels	Auxiliary boat	Cable layer		Independent from miscellaneous ship

Minesweeper

Minesweeper No. 4

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
1 April 1920	Auxiliary vessels	Auxiliary boat	Minesweeper	1st class minesweeper	And over 500 tons designated displacement
				2nd class minesweeper	Less than 500 tons designated displacement
30 June 1923	Naval vessels		Minesweeper		'Class' was abolished

Auxiliary minesweeper

Auxiliary minesweeper No. 1

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
30 June 1923	Auxiliary vessels	Auxiliary boat	Auxiliary minesweeper	1st class auxiliary minesweeper	And over 500 tons designated displacement
				2nd class auxiliary minesweeper	Less than 500 tons designated displacement
30 May 1931	Auxiliary vessels	Auxiliary boat	Auxiliary minesweeper		'Class' was abolished

Submarine chaser

Submarine chaser No. 8

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
23 May 1933	Auxiliary vessels	Auxiliary boat	Submarine chaser
1 April 1940	Naval vessels		Submarine chaser

Auxiliary submarine chaser

Auxiliary submarine chaser No. 1 class

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
1 April 1940	Auxiliary vessels	Auxiliary boat	Auxiliary submarine chaser		Divided from submarine chaser

Patrol boat

Patrol boat No. 35

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
30 March 1940	Auxiliary vessels	Auxiliary boat	Patrol boat
15 February 1943	Naval vessels		Patrol boat

Auxiliary patrol boat

Auxiliary patrol boat No. 173

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
15 February 1943	Auxiliary vessels	Auxiliary boat	Auxiliary patrol boat		Divided from patrol boat

Landing ship

2nd class landing ship No. 151

• Note 1; pertinence of 1st class landing ship was only No.1 class.
• Note 2; pertinence of 2nd class lamding ship was only No.101 class.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
5 February 1944	Naval vessels		Landing ship	1st class landing ship	And over 1,000 tons displacement
				2nd class landing ship	Less than 1,000 tons designated displacement

Motor torpedo boat

Motor torpedo boat No. 2

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
30 June 1941	Auxiliary vessels	Auxiliary boat	Motor torpedo boat		Independent from miscellaneous ship

Transport vessel/Transport ship

Transport vessel (Oiler) Hayatomo

• Note; Included replenishment oiler (給油船/給油艦, Kyūyusen/Kyūyukan), collier (給炭船/給炭艦, Kyūtansen/Kyūtankan), collier-oiler (給炭油艦, Kyūtan'yukan), munition ship (給兵艦, Kyūheikan), food supply ship (給糧艦, Kyūryōkan) and freighter (雑用艦, Zatsuyōkan).

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
5 October 1872	Transport vessel		4th class transport vessel		And over 800 tons displacement
			5th class transport vessel		And over 500 tons displacement
			6th class transport vessel		And over 200 tons displacement
			7th class transport vessel		And under 200 tons displacement
13 August 1890	Vessels	Category 'D' warship	Transport ship
1 April 1896	Vessels	Miscellaneous ships	Transport ship
12 December 1905			Transport ship		Independent from miscellaneous ships
17 May 1916	Auxiliary ships		Transport ship
1 April 1920	Auxiliary vessels	Auxiliary vessel	Transport vessel

Icebreaker

Icebreaker Ōtomari

• Note; pertinence of icebreaker was only Ōtomari.

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
3 August 1921	Auxiliary vessels	Auxiliary vessel	Icebreaker

Survey ship

Survey ship Tsukushi

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
31 March 1922	Auxiliary vessels	Auxiliary vessel	Survey ship

Target ship

• This section treats a self-propelled target ship. Towed target ship is miscellaneous ship.

Target ship Settsu

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
29 September 1923	Auxiliary vessels	Auxiliary vessel	Target ship

Auxiliary training ship

Auxiliary training ship Shikishima

Date	Top classification	Higher classification	Classification	Lower classification	Note, classification boundary
30 November 1922	Auxiliary vessels	Auxiliary vessel	Auxiliary training ship

Appendix

Footnotes

See also

• Japanese ship-naming conventions
• List of ships of the Imperial Japanese Navy
• List of Japanese Navy ships and war vessels in World War II

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