In the 2020 COVID-19 stock market crash, the S&P 500 took 16 trading days to fall from its record high into a bear market.
The index reached a closing record on February 19, 2020. By March 12, it had fallen at least 20% from that high, meeting the common definition of a bear market. The speed of the decline made it one of the fastest bear-market transitions in modern U.S. market history.
The sell-off reflected growing concern about the spread of COVID-19, business shutdowns, travel restrictions, supply disruptions, and the likely economic effects of the pandemic. Energy markets also came under pressure after an oil-price dispute between Saudi Arabia and Russia.
The crash was followed by an exceptionally rapid rebound after central-bank actions, government support, vaccine progress, and improving investor expectations. A bear market is normally measured from a peak to a decline of at least 20%; it does not necessarily mean that prices have reached their ultimate low.