Dow drops 7.8% -- or more than 2,000 points -- the worst fall since 2008, almost ending an 11-year bull market.
The drop came as a free-fall in oil prices and worsening fears of fallout from the spreading coronavirus outbreak seizes markets.
The sharp drops triggered the first automatic halts in trading in two decades.
The price of oil plunged nearly 25% after Saudi Arabia indicated it would ramp up production after Russia refused to production cutbacks in response to falling demand. Europe fell into a bear market. U.S. stocks are now down 19% from the peak they reached last month. Bond yields plumbed new lows as investors sought safety.