The SPDR S&P 500 ETF Trust (SPY) is an exchange-traded fund (ETF) that tracks the performance of the S&P 500 Index. The fund is managed by State Street Global Advisors and was launched in 1993.

The S&P 500 Index is a market-capitalization-weighted index that measures the performance of the 500 largest U.S. publicly traded companies. The index is a popular benchmark for many investors.

SPY is the most popular ETF in the world, with over 300 billion USD in assets under management. The fund has a low expense ratio.