Chōgei (長鯨, Long Whale),[1] was the second and final vessel of the Jingei-class submarine tenders operated by the Imperial Japanese Navy, from the 1920s through World War II.

Initially, Chōgei was planned as a 14,500-ton vessel; however, her specifications were scaled down to 8,500-tons due to restrictions imposed by the Washington Naval Treaty.

In order to keep costs to a minimum, the basic design of her hull was adapted from that of a standard civilian merchant vessel, of which Mitsubishi had considerable experience in building.

Renovations were begun on Chōgei in November 1934 at the Sasebo Naval Arsenal to equip the vessel with new ballast tanks and bilge pumps.

Aside from duty as a troop transport, shuttling between Shanghai and Port Arthur, Chōgei took no further combat role in the Second Sino-Japanese War.

[2] On 15 November 1940, in preparation for the coming conflict with the United States, both Jingei-class ships were returned to active combat status, replacing Takasaki and Tsuruguzaki, which were then converted to aircraft carriers.

[2] Following the start of the Pacific War, Chōgei was based at Davao in the Philippines and was assigned a patrol area stretching to the Celebes, and south to the Flores Sea and Torres Straits.

However, the repeated air raids led the Imperial Japanese Navy to order the withdrawal of Chōgei back to Japan.