KDDI Corporation (KDDI株式会社, KDDI Kabushiki Gaisha) (TYO: 9433) is a Japanese telecommunications operator formed in October 1, 2000 through the merger of DDI Corp. (Daini-Denden Inc.), KDD (Kokusai Denshin Denwa) Corp., and IDO Corp. It has its headquarters in the Garden Air Tower in Iidabashi, Chiyoda, Tokyo.KDDI provides mobile cellular services using the "au by KDDI" brand.