On June 1, 2018, the European Central Bank (ECB) celebrated its 20th anniversary. This paper provides a comprehensive view of the ECB's monetary policy over these two decades. The first section gives a chronological account of the macroeconomic and monetary policy developments in the euro area since the adoption of the euro in 1999, going through four cyclical phases "conditioning" ECB monetary policy. We describe the monetary policy decisions from the ECB's perspective and against the background of its evolving monetary policy strategy and framework. We also highlight a number of the key, critical issues that were the subject of debate. The second section contains various assessments. We analyze the achievement of the price stability mandate and developments in the ECB's credibility, and we also investigate the ECB's interest rate decisions through the lens of a simple empirical interest rate reaction function. Finally, we present the ECB's framework for thinking about nonstandard monetary policy measures and review the evidence on their effectiveness. One of the main themes of the paper is how the ECB utilized its monetary policy to respond to the challenges posed by the European twin financial and sovereign debt crises and the subsequent slow economic recovery, making use of its relatively wide range of instruments, defining new ones where necessary, and developing the strategic underpinnings of its policy framework.