Chevron Corporation is an American multinational energy corporation headquartered in San Ramon, California, United States and active in more than 180 countries. It is engaged in every aspect of the oil, gas, and geothermal energy industries, including exploration and production; refining, marketing and transport; chemicals manufacturing and sales; and power generation. Chevron is one of the world’s six “supermajor” oil companies. For the past five years, Chevron has been continuously ranked as one of America’s 5 largest corporations by Fortune 500 and it is currently ranked 3rd after ExxonMobil and Walmart. In 2011 it was named the 16th largest public company in the world by Forbes Global 2000. Chevron is one of the largest corporations in the world by revenue.