Citadel LLC (formerly known as Citadel Investment Group, LLC) is an American multinational hedge fund and financial services company. Founded in 1990 by Kenneth Griffin, it has more than $65 billion in assets under management as of January 2025. The company has over 2,900 employees, with corporate headquarters in Miami, Florida,^: 1 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.

Citadel LLC is a separate entity from the market maker Citadel Securities, although both were founded and are owned by Griffin.