For most of the decade before the COVID-19 pandemic, undershooting rather than overshooting had been the main inflation problem of the European Central Bank (ECB). During 2020, consumer prices in the euro area were falling; by the end of that year, average inflation since the introduction of the euro two decades earlier stood at only 1.6 percent per year. Things began to snowball in 2021. The 12-month inflation rate steadily accelerated. It reached double digits in the final quarter of 2022—more than twice the level it had ever reached since the euro’s introduction in 1999. Four striking features emerge from a review of the unexpected surge in European inflation since 2021: (1) The ECB’s monetary policy response lagged behind that of the US Federal Reserve, reflecting the more gradual evolution of inflation in the euro area and its distinct pattern of causes; (2) the range of inflation rates across different euro area countries has been unprecedented. This largely reflects the differential impact of war-related energy shocks (especially for natural gas piped from Russia) as well as the differential fiscal response by national governments partially insulating consumers from these shocks; (3) not all households were net losers from the inflation, with some benefiting from the fact that inflation reduced the real value of their indebtedness; and (4) the speed with which inflation was returning toward target during 2023 prompted concerns that the ECB’s monetary tightening might have been pushed too far, prolonging the output slowdown.