Citadel LLC is a privately owned American multinational hedge fund and financial services company headquartered in Chicago, Illinois. Founded in 1990 by billionaire Kenneth C. Griffin, Citadel has grown to become one of the largest hedge funds globally, with over $39 billion in assets under management as of 2021. The company employs over 4,060 people and offers various financial services, including investment management, market making, and securities trading. Citadel is known for its quantitative trading strategies and has been recognized for its strong performance and risk management capabilities.