Citadel LLC is an American multinational hedge fund and financial services company. Founded in 1990 by Ken Griffin, it has more than $58 billion in assets under management as of January 2024. The company has over 2,800 employees, with corporate headquarters in Miami, Florida, and offices throughout North America, Asia, and Europe. Founder, CEO and Co-CIO Griffin owns approximately 85% of the firm. As of December 2022, Citadel is one of the most profitable hedge funds in the world, posting $74 billion in net gains since its inception in 1990, making it the most successful hedge fund in history, according to CNBC.

A hedge fund is a pooled investment fund that holds liquid assets and that makes use of complex trading and risk management techniques to improve investment performance and insulate returns from market risk. Among these portfolio techniques are short selling and the use of leverage and derivative instruments. In the United States, financial regulations require that hedge funds be marketed only to institutional investors and high-net-worth individuals.