The Japanese naval task force that attacked Pearl Harbor was called the Kido Butai.
Kido Butai is commonly translated as “Mobile Force.” It was the Japanese First Air Fleet’s carrier striking force, organized to project concentrated air power across the Pacific. For the Pearl Harbor operation, it included six aircraft carriers supported by battleships, cruisers, destroyers, submarines, and supply vessels.
Vice Admiral Chūichi Nagumo commanded the force at sea, while Admiral Isoroku Yamamoto organized and advocated the broader operation as commander of Japan’s Combined Fleet. The task force departed Hitokappu Bay in the Kuril Islands in November 1941 and crossed the North Pacific under strict radio silence.
Kido Butai is sometimes incorrectly used as though it meant the entire Japanese Navy. It referred specifically to the mobile carrier force assembled for major operations. After Pearl Harbor, it was used in other campaigns before suffering heavy losses at Midway.