Citadel Securities is a global market-making firm founded in 2002, headquartered in Chicago. It provides liquidity in equities, options, and fixed income products, serving institutional and retail investors. The company is recognized for its advanced trading technology and high-frequency trading strategies, playing a significant role in U.S. and international market structure. Citadel Securities is a separate entity from Citadel LLC, the hedge fund founded by Ken Griffin.