The S&P 500 is a stock market index tracking the stock performance of 500 companies listed on stock exchanges in the United States that are considered to have large market capitalizations. The S&P 500 is a subset of the S&P 1500. It is maintained by S&P Dow Jones Indices and its components are selected by a committee.
The index is a public-float-weighted/capitalization-weighted index. The index includes approximately 83% of the total market capitalization of U.S. public companies, with an aggregate market capitalization of more than $61.1 trillion as of December 31, 2025. The median market capitalization of the components of the index is $41.8 billion and components range in market capitalization from $5.6 billion to $4.8 trillion.
Products linked to the S&P 500 include index funds as well as derivatives, which are available for trading in many countries with the goal of replicating the performance of the index.Wikipedia