Citadel Securities LLC is an American market making firm providing liquidity and trade execution to retail and institutional clients, headquartered in Miami.

[17] In 2008, Citadel Securities hired 70 people and Rohit D'Souza, a banker from Merrill Lynch, who left after eight months "to build an investment bank" and brokerage.

[30] They delayed certain equity orders from clients to buy or sell shares while continuing to trade the same stocks in its own account as part of its market-making activities, according to FINRA.

[31] During the coronavirus pandemic, the firm doubled its profit while generating $4 billion in revenue during the first half of 2020 due to an increase in volatility and retail trading.

[42][43] That same month, President Biden's nominee for SEC Chairman, Gary Gensler, raised further concerns about Citadel's dominant market position at a congressional hearing in March, asking: "one firm now has 40% to 50% of the retail order flow, what does that do to pricing of capital in this country?

[45] In light of Citadel Securities' role in the GameStop short squeeze event, individuals such as Senator Elizabeth Warren have raised concerns about several potential conflicts of interest.

[47] In November 2021, a U.S. District Court dismissed a class action lawsuit, ruling that investors failed to show collusion between Robinhood and Citadel.

[48] In March, Citadel's payment-for-order-flow arrangements with brokerages such as Robinhood was heavily criticized during Congressional hearings on the GameStop short squeeze.

[49] Citadel's practice of hiring officials from agencies that regulate it, including the SEC and the CFTC, as well its relationships with Ben Bernanke and Janet Yellen, has also been widely observed and attracted concerns about conflicts of interest.

[57] As of February 2023, the Hong Kong based subsidiary of Citadel Securities was designated as a "qualified foreign institutional investor" or QFII, by the Chinese government, giving the company more access to mainland China's bond and stock markets.

The SEC found that, between 2015 and 2020, Citadel Securities mismarked millions of sell orders due to a coding error in their automated trading system, obstructing regulatory oversight.

[62] In September 2024, Citadel Securities hired Jim Esposito, former co-head of global banking and markets at Goldman Sachs, as president.

[65] According to the Wall Street Journal, about one-third of stock orders from individual investors in 2015 was completed through Citadel, which accounts for about 10 percent of the firm's revenue.