The 2d Antiaircraft Artillery Battalion (2d AAA Bn) was a United States Marine Corps antiaircraft unit that served during World War II. Formed in 1940 as the 2d Defense Battalion, its original mission was to provide air and coastal defense for advanced naval bases. During the war the battalion defended Hawaii, Tutuila in American Samoa and Guam and took part in combat operations at Tarawa Atoll and Okinawa. The battalion returned to the United States after the war and was decommissioned at Marine Corps Base Camp Pendleton, California on 28 November 1945.