# Sōryū-class submarine

The Sōryū-class submarines (16SS) are diesel-electric attack submarines. The first boat in the class entered service with the Japan Maritime Self-Defense Force in 2009. The design is an evolution of the Oyashio class, from which it can most easily be distinguished by its X-shaped stern combination diving planes and rudders. At the time of launching, the Sōryūs had the largest displacement of any submarine used by post-war Japan.
The Sōryū-class is Japan's first air-independent propulsion submarine class. From Sōryū to Shōryū are fitted with Kockums Naval Solutions Stirling engines license-built by Kawasaki Heavy Industries, allowing them to stay submerged for longer periods of time. The 11th submarine of the class, Ōryū, is the world's first lithium-ion battery submarine. The cost of the sixth submarine (Kokuryū) was estimated at US$540 million.
In 2023, the first of the replacements for the Sōryūs, the Taigei class, entered service.

## Naming convention

Japanese submarines since World War II were named after ocean currents. The JMSDF changed its naming convention with the Sōryū, and submarines will now be named after mythological creatures. Sōryū (そうりゅう) means blue dragon in Japanese and shares its name with the World War II aircraft carrier Sōryū, sunk during the Battle of Midway.

## Variants

The eleventh Sōryū-class submarine (Ōryū) is the first Japanese submarine in the fleet to mount lithium-ion batteries. The JS Ōryū was given a budget of ¥64.3 billion (equivalent to ¥65.55 billion or US$601.3 million in 2019) under the 2015 Japanese Defense Budget.
Lithium-ion batteries have almost twice the electric storage capacity of traditional lead-acid batteries. Updated Sōryū-class boats also added more batteries by placing them within hull spaces previously occupied by AIP system machinery. These upgraded boats benefited by increasing both the size and energy density of their battery storage. The change to lithium-ion improved the underwater endurance significantly and will be an advantage over the slow recharge capability of the AIP system.
In any event, JMSDF believes that lithium-ion is the way forward and intends to 'trial' this new system and compare it to the previous AIP system for operational effectiveness.

## Exports

Japan offered Sōryū-class submarines to Australia as replacements for the Royal Australian Navy's Collins-class submarines, as part of the Collins-class submarine replacement project. On 9 April 2014, then-Australian Minister for Defence, David Johnston, described the Sōryū class as "extremely impressive" while discussing Australia's future submarine options. On 26 April 2016, Australian Prime Minister Malcolm Turnbull announced that the Australian contract had been awarded to the French-designed Shortfin Barracuda, though this deal was eventually rescinded.
India, Morocco, Norway, Netherlands, and Taiwan have also approached Japan, and expressed an interest in buying Sōryū-class submarines. During a visit to Japan, India's then-Union Minister of Defence, Manohar Parrikar, invited the Japanese government to participate in their US$8.1 billion Project 75I-class submarine procurement program.
* Zuiryū (SS-505) under construction
* Hakuryū (SS-503) visiting Guam in 2013

## Boats

| Project no. | Building no. | Pennant no. | Name | Japanese | Namesake | Laid down | Launched | Commissioned | Home port | Notes |
| S131 | 8116 | SS-501 | Sōryū | そうりゅう | Blue Dragon | 31 March 2005 | 5 December 2007 | 30 March 2009 | Kure | |
| S131 | 8117 | SS-502 | Unryū | うんりゅう | Cloud Dragon | 31 March 2006 | 15 October 2008 | 25 March 2010 | Kure | These five submarines are equipped with a new sonar ZQQ-7B. |
| S131 | 8118 | SS-503 | Hakuryū | はくりゅう | White Dragon | 6 February 2007 | 16 October 2009 | 14 March 2011 | Kure | These five submarines are equipped with a new sonar ZQQ-7B. |
| S131 | 8119 | SS-504 | Kenryū | けんりゅう | Sword Dragon | 31 March 2008 | 15 November 2010 | 16 March 2012 | Kure | These five submarines are equipped with a new sonar ZQQ-7B. |
| S131 | 8120 | SS-505 | Zuiryū | ずいりゅう | Auspicious Dragon | 16 March 2009 | 20 October 2011 | 6 March 2013 | Yokosuka | These five submarines are equipped with a new sonar ZQQ-7B. |
| S131 | 8121 | SS-506 | Kokuryū | こくりゅう | Black Dragon | 21 January 2011 | 31 October 2013 | 9 March 2015 | Yokosuka | These five submarines are equipped with a new sonar ZQQ-7B. |
| S131 | 8122 | SS-507 | Jinryū | じんりゅう | Benevolent Dragon | 14 February 2012 | 8 October 2014 | 7 March 2016 | Kure | This submarine is equipped with a new sonar ZQQ-7B and a new satellite communication device. |
| S131 | 8123 | SS-508 | Sekiryū | せきりゅう | Red Dragon | 15 March 2013 | 2 November 2015 | 13 March 2017 | Kure | This submarine is equipped with a new sonar ZQQ-7B, a new satellite communication device and new torpedo counter measures. |
| S131 | 8124 | SS-509 | Seiryū | せいりゅう | Pure Dragon | 22 October 2013 | 12 October 2016 | 12 March 2018 | Yokosuka | |
| S131 | 8125 | SS-510 | Shōryū | しょうりゅう | Soaring Dragon | 28 January 2015 | 6 November 2017 | 18 March 2019 | Kure | |
| S131 | 8126 | SS-511 | Ōryū | おうりゅう | Phoenix Dragon | 16 November 2015 | 4 October 2018 | 5 March 2020 | Kure | These two submarines utilize Li-ion battery propulsion technology |
| S131 | 8127 | SS-512 | Tōryū | とうりゅう | Fighting Dragon | 27 January 2017 | 6 November 2019 | 24 March 2021 | Yokosuka | These two submarines utilize Li-ion battery propulsion technology |