Kaga was an aircraft carrier built for the Imperial Japanese Navy (IJN) and was named after the former Kaga Province in present-day Ishikawa Prefecture. Originally intended to be one of two Tosa-class battleships; Kaga was converted under the terms of the Washington Naval Treaty to an aircraft carrier as the replacement for the battlecruiser Amagi; which had been damaged during the 1923 Great Kanto earthquake. Kaga was rebuilt in 1933-35; increasing her top speed; improving her exhaust systems; and adapting her flight decks to more modern; heavier aircraft.

Kaga's aircraft first supported Japanese troops in China during the Shanghai Incident of 1932 and participated in the Second Sino-Japanese War in the late 1930s. With other carriers; she took part in the Pearl Harbor raid in December 1941 and the invasion of Rabaul in the Southwest Pacific in January 1942. The following month her aircraft participated in a combined carrier airstrike on Darwin; Australia; helping secure the conquest of the Dutch East Indies by Japanese forces.

Following repairs; Kaga rejoined the 1st Air Fleet for the Battle of Midway in June 1942. After bombarding American forces on Midway Atoll; Kaga and three other IJN carriers were attacked by American aircraft from Midway and the carriers Enterprise; Hornet; and Yorktown. Dive bombers from Enterprise severely damaged Kaga; when it became obvious she could not be saved; she was scuttled by Japanese destroyers to prevent her from falling into enemy hands.

The loss of four large attack carriers; including Kaga at Midway; was a crucial setback for Japan; and contributed significantly to Japan's ultimate defeat. In 1999; debris from Kaga including a large section of the hull was located on the ocean floor at a depth in excess of 5;000 meters (16;404 ft); 350 miles (560 km) northwest of Midway Island. The main part of the carrier's wreck has not been found.