Concerns about the spread of the COVID-19 virus and its effect on economic activity produced one of the most turbulent periods of financial market activity in history from mid-February to April 2020. In some ways, this episode resembled the events of September-October 2008, during the Global Financial Crisis (GFC) of 2007-09. Severe problems arose suddenly in international financial markets. Uncertainty and fear raised volatility and led investors to broadly sell risky assets, which reduced their prices. International authorities responded to both the GFC and the recent COVID-19-inspired crisis. Fiscal authorities increased spending, including providing much more generous unemployment benefits, while central banks made credit more widely available in financial markets and supported markets for illiquid securities. Regulators allowed banks to reduce their capital and liquidity buffers and encouraged lenders to work with borrowers. But there are significant differences between the two events, too. The events of September 2008 resembled a bank run. Investors became uncertain about the value of some types of risky housing assets-mortgage-backed securities (MBS) and other asset-backed securities (ABS) not guaranteed by the government and collateralized debt obligations-and therefore sought to reduce their exposure to all such assets and the firms that might own them or have guaranteed them. This article reviews and explains the recent policy reactions of the Federal Reserve, the European Central Bank, the Bank of England, and the Bank of Japan to the financial and macroeconomic turmoil caused by the COVID-19 pandemic. The financial and monetary policy actions of major central banks in the most recent crisis have, by some metrics, surpassed their responses to the Global Financial Crisis of 2007-09 in both swiftness and scope. (JEL E58, E59, G01, E44, G15)