The COVID-19 pandemic triggered the 2020 stock-market crash after the World Health Organization declared a pandemic.
The WHO characterized COVID-19 as a pandemic on 11 March 2020. Governments introduced travel restrictions, business closures, and stay-at-home measures as infections spread, creating a sudden shock to demand, employment, supply chains, and corporate earnings.
The S&P 500 entered a bear market in March, and trading was halted temporarily several times by market-wide circuit breakers. On 16 March 2020, the index fell 11.98%, its largest one-day percentage decline since 1987. Central banks and governments responded with major monetary and fiscal support.
The crash was not caused by a single company failure. It reflected the economic consequences of a public-health emergency, compounded by an oil-price dispute and severe uncertainty. Markets later rebounded sharply, though the economic and health effects continued.