India's Securities and Exchange Board (SEBI) has temporarily barred U.S.-based quantitative trading firm Jane Street from accessing the country's securities market following an investigation into alleged market manipulation. SEBI's probe found that Jane Street engaged in manipulative trading strategies involving Bank Nifty and Nifty 50 index derivatives, particularly on expiry days, which led to unlawful gains estimated at approximately ₹4,843 crore (around $570 million). The regulator has directed banks to freeze Jane Street's accounts and has ordered the firm to disgorge these unlawful profits. Jane Street reportedly generated over $4.3 billion in trading gains in India over the past two years, with a net revenue of more than $2.3 billion from equity derivatives last year alone. The ban is considered one of the most stringent actions taken by Indian authorities against a foreign trading firm. SEBI is expanding its investigation to include other indices and exchanges to examine potential further manipulation. Jane Street has contested the charges, describing its trading activities as basic index arbitrage and plans to legally challenge the ban and allegations. The crackdown has raised concerns about liquidity and trading volumes in India's derivatives market, although SEBI sources indicate it may promote more responsible investing. Additionally, SEBI released a study revealing that 91% of retail traders in India's equity derivatives segment incurred losses totaling over ₹1 lakh crore ($12.2 billion) in fiscal year 2025. The Jane Street case has also sparked discussions about regulatory oversight and structural vulnerabilities within India's derivatives market.