Citadel Securities LLC

Citadel Securities LLC is a global financial market-making firm headquartered in Miami, Florida, having moved from Chicago in 2022. Founded in 2002 by Kenneth C. Griffin, the company is privately held, with Griffin holding a majority stake. In 2022, Citadel Securities received a $1.15 billion minority investment from Sequoia Capital and Paradigm, valuing the firm at approximately $22 billion. The company reported approximately 2,300-2,500 employees as of late 2025/early 2026 and generated approximately $12.2 billion in trading revenue in 2025.

Citadel Securities operates as a next-generation capital markets firm, providing critical liquidity and trade execution services to retail and institutional clients worldwide. It specializes in market making across a broad array of asset classes, including equities, options, fixed income (such as U.S. Treasuries, interest rate swaps, and corporate debt), currencies, and futures. The firm is the largest designated market maker on the New York Stock Exchange, a leading U.S. options market maker, and a significant ETF trader. Leveraging advanced technology, quantitative research, machine learning, and AI, Citadel Securities executes approximately 35% of all U.S.-listed retail volume.

In terms of patent litigation, Citadel Securities LLC appears to be an active litigant, engaging in both defense and assertion of patent rights. The company has been involved in two tracked cases: one as a plaintiff and one as a defendant. Both cases involve HFT Solutions LLC, with Citadel Securities being sued by HFT Solutions LLC in the U.S. District Court for the Northern District of Illinois in December 2024, and subsequently challenging HFT Solutions LLC's patent at the Patent Trial and Appeal Board (PTAB) in December 2025. This posture suggests an operating company proactively managing intellectual property related to its core high-frequency trading (HFT) operations.