Citadel (formerly known as Citadel Investment Group, LLC) is an American global financial institution. Founded in 1990 by Kenneth C. Griffin, the company operates two primary businesses: Citadel, one of the world's largest alternative asset managers with more than $25 billion in assets under management; and Citadel Securities, one of the leading market makers in the world, trading products including equities, equity options, and interest rate swaps for retail and institutional clients.[3]

Citadel is one of only three percent of hedge funds that have been in existence for more than 20 years. Recognized for its investment performance, the firm manages assets for many of the world's largest institutional investors including sovereign wealth funds, pensions, and university endowments.[4] The company has more than 1400 employees, with headquarters in Chicago, and offices throughout North America, Asia and Europe.[5]

https://en.wikipedia.org/wiki/Citadel_LLC