The National Iranian South Oil Company (NISOC; ) is a government-owned corporation under the direction of the Ministry of Petroleum of Iran, and operates as a subsidiary of National Iranian Oil Company. It was established in Masjed Soleyman, 1971. Currently NISOC is Iran's biggest oil producer, and the company is active in a land area more than 400,000 km² with headquarters in Ahvaz, Iran and other nine subsidiaries. NISOC is producing about 83% of all crude oil and 16% of natural gas produced in Iran and ranks as the Iran's largest oil company.