Kawachi () was the lead ship of her class of two Kawachi-class dreadnought battleships built for the Imperial Japanese Navy (IJN) in the 1910s. Completed in 1912, she often served as a flagship. Her only combat action during World War I was when she bombarded German fortifications in China during the Battle of Tsingtao in 1914. She sank in 1918 after an explosion in her ammunition magazine with the loss of over 600 officers and crewmen.

The Imperial Japanese Navy (IJN; Kyūjitai: 大日本帝國海軍 Shinjitai: 大日本帝国海軍 Dai-Nippon Teikoku Kaigun 'Navy of the Greater Japanese Empire', or 日本海軍 Nippon Kaigun, 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender in World War II. The Japan Maritime Self-Defense Force (JMSDF) was formed between 1952–1954 after the dissolution of the IJN.The Imperial Japanese Navy was the third largest navy in the world by 1920, behind the Royal Navy and the United States Navy (USN). It was supported by the Imperial Japanese Navy Air Service for aircraft and airstrike operation from the fleet. It was the primary opponent of the Western Allies in the Pacific War.

The origins of the Imperial Japanese Navy go back to early interactions with nations on the Asian continent, beginning in the early medieval period and reaching a peak of activity during the 16th and 17th centuries at a time of cultural exchange with European powers during the Age of Discovery. After two centuries of stagnation during the country's ensuing seclusion policy under the shōgun of the Edo period, Japan's navy was comparatively backward when the country was forced open to trade by American intervention in 1854. This eventually led to the Meiji Restoration. Accompanying the re-ascendance of the Emperor came a period of frantic modernization and industrialization. The navy had several successes, sometimes against much more powerful enemies such as in the Sino-Japanese War and the Russo-Japanese War, before being largely destroyed in World War II.