SPX500 is the stock market symbol for the S&P 500 index, which is a stock market index that measures the stock performance of 500 large companies listed on stock exchanges in the United States. The S&P 500 is one of the most widely followed stock market indices in the world and is considered to be a good indicator of the overall health of the U.S. economy. The SPX500 can be traded as a financial instrument through derivatives such as contracts for difference (CFDs) or exchange-traded funds (ETFs).