The 1st Air Fleet (第一航空艦隊, Daiichi Kōkū Kantai) also known as the Kidō Butai ("Mobile Force"), was a name used for a combined carrier battle group comprising most of the aircraft carriers and carrier air groups of the Imperial Japanese Navy (IJN), during the first eight months of the Pacific War.
At the time of its best-known operation, the attack on Pearl Harbor, in December 1941, the 1st Air Fleet was the world's largest fleet of aircraft carriers.