Shell Oil Company is the United States-based subsidiary of Royal Dutch Shell. Its parent is a multinational oil company ("oil major") of Anglo Dutch origins. Royal Dutch Shell is one of the largest oil companies in the world. About 22,000 Shell employees are based in the United States The head office in the United States is in Houston, Texas. Shell Oil Company, including its related companies, is one of the US’s largest oil and natural gas producers, natural gas marketers, gasoline marketers and petrochemical manufacturers.