Ōi (大井) was the fourth of five Kuma-class light cruiser, which served in the Imperial Japanese Navy during World War II.

At the time of the Shanghai Incident of 1932, Ōi was reassigned to patrols of the China coast, but she resumed her training role from the end of 1933 to mid-1937.

[4] During the attack on Pearl Harbor of 7 December 1941, Ōi escorted the battleship force of the Combined Fleet from its anchorage at Hashirajima in Hiroshima Bay to the Bonin Islands and back.

[5] While the Imperial Japanese Navy General Staff debated the issue, Ōi was assigned to escorting transports between Hiroshima and Mako, Pescadores Islands from the end of January through mid-April.

On 29 May, during the Battle of Midway, Ōi was part of Vice Admiral Shirō Takasu's (Aleutian Screening) force, and returned safely to Yokosuka Naval District on 17 June.

[4] From the end of October through most of December, Ōi ferried troops and supplies from Truk and Manila to Rabaul, New Britain and Buin, Bougainville.

While at Makassar on 23 June, she was attacked by Consolidated Aircraft B-24 Liberator heavy bombers of the USAAF 5th Air Force's 319th Bombardment Squadron, but she was not damaged.

During the month of May, Ōi was primarily involved in troop transport operations between Tarakan, Palau and Sorong, and in June she was reassigned to patrols in the Java Sea.

When the cruiser was 1,400 yd (1,300 m) astern, Flasher fired her four stern tubes, hitting Ōi with two torpedoes portside aft.