The "September Curse" is a notorious stock market trend where the S&P 500 often underperforms in September, averaging a -1% return since 1928. Historical data, seasonal factors like post-summer portfolio rebalancing, and a lack of earnings reports drive this dip. Investor psychology also amplifies the curse, creating a self-fulfilling prophecy. Notable examples include the 2008 financial crisis (-9%) and 2022’s inflation-driven drop (-9.2%). While not every September tanks, the curse’s reputation persists. Stay calm, diversify, and focus on long-term investing to navigate this spooky market season without fear.