Indian Oil Corporation Limited (IOCL), commonly known as IndianOil is an Indian state owned oil and gas company with registered office at Mumbai and primarily headquartered in New Delhi. It is the largest commercial oil company in the country, with a net profit of INR 19,106 crore (USD 2,848 million) for the financial year 2016–17. It is ranked 1st in Fortune India 500 list for year 2016 and 168th in Fortune's ‘Global 500’ list of world's largest companies in the year 2017. As of 31 March 2017 IndianOil's employee strength is 33,135, out of which 16,545 are in the officer cadre. It is India's largest downstream oil company, with a work force of more than 33,000 employees, a turnover of Rs. 506,428 crore and a net profit of Rs. 21,346 crore in 2017-18.

IndianOil's business interests overlap the entire hydrocarbon value-chain, including refining, pipeline transportation, marketing of petroleum products, exploration and production of crude oil, natural gas and petrochemicals.

IndianOil has ventured into alternative energy and globalization of downstream operations. It has subsidiaries in Sri Lanka (Lanka IOC), Mauritius (IndianOil (Mauritius) Ltd) and the Middle East (IOC Middle East FZE).

In May 2018, IOC become India's most profitable state-owned company for the second consecutive year, with a record profit of Rs. 21,346 crore in 2017-18, followed by Oil and Natural Gas Corporation, whose profit stood at Rs. 19,945 crore.