While you can’t invest directly in the S&P 500 index itself, you can invest in funds that track it. These funds are called S&P 500 Index Funds or S&P 500 Exchange-Traded Funds (ETFs). They aim to replicate the performance of the S&P 500 index, which includes 500 of the largest US companies listed on stock exchanges in the US. There are also mutual funds that carry S&P 500 stocks you can invest in, or at many brokerages, you can invest directly in stocks that are in the S&P 500.