You can sell short S&P 500 ETFs like the S&P 500 Index (SPY). But this strategy can be risky, since losses on short positions in stocks, ETFs, or stock index futures are potentially unlimited, and may be subject to margin calls. However, there are times when a bearish bet against a benchmark stock index, such as the S&P 500, is appropriate. Buying Puts is one option, get it! also otm put calendar debit spreads may be worth watching.