The S&P 500, or "the S&P", is a stock market index that tracks the performance of 500 of the largest publicly traded companies in the US. This benchmark index is a key indicator of the overall health and stability of the U.S. stock market. It acts as a snapshot of the nation's leading businesses across various sectors, making it a valuable resource for investors and analysts. This index is run by: S&P 500 Dow Jones Indices