What was the name of the U.S. futures contract whose large sell order helped trigger the 2010 Flash Crash?

An E-mini S&P 500 futures contract was involved in the large sell order that helped trigger the 2010 Flash Crash.

E-mini S&P 500 futures are electronically traded contracts whose value is linked to the S&P 500 index. They allow investors to gain or reduce broad U.S. equity exposure with less capital than a full-sized futures contract. By 2010, these contracts were among the most actively traded instruments in global markets.

The U.S. Securities and Exchange Commission and the Commodity Futures Trading Commission concluded that a large automated sell order in E-mini S&P 500 futures interacted with high-frequency trading and fragmented liquidity. Selling pressure moved between futures and cash markets, accelerating the decline.

The contract was not the only cause. Investigators described a chain of interactions involving execution algorithms, market makers, and temporary withdrawal of liquidity. The episode showed why identifying a single “trigger” is different from explaining the full mechanism of a market crash.