Citadel Securities LLC is an American market making firm headquartered in Miami. It is one of the largest market makers in the world, and is active in more than 50 countries. It is the largest designated market maker on the New York Stock Exchange.

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.