Mitsui Oil Exploration Co., Ltd. (三井石油開発株式会社, Mitsui Sekiyu Kaihatsu Kabushiki-gaisha) (MOECO) is an oil exploration subsidiary of Mitsui & Co. that specializes in natural gas. It has its headquarters in the Hibiya Central Building in Nishi-Shinbashi, Minato, Tokyo. It was one of 17 Mitsui companies that were spun off on July 19, 1969.