Mitsui & Co. Energy Marketing and Services ("MEMS") is a subsidiary of Mitsui & Co., Ltd. ("Mitsui"), a diversified global trading, investment, and service enterprise headquartered in Tokyo, Japan. Mitsui mantains a global network of 139 offices in 66 countries/regions and has 491 group companies and associated companies worldwide.

With the United States the new epicenter of the energy business, Mitsui is aiming to build a US-based marketing and trading platform for everything from gas to electric power. Since its inception, MEMS has been expanding the scope and scale of its activities in line with that mission. The company started out performing a single function: the marketing of equity gas from the Marcellus shale to major population centers in the northeastern United States such as New York and New Jersey.