The European Central Bank (ECB) is the central component of the Eurosystem and the European System of Central Banks (ESCB) as well as one of seven institutions of the European Union. It is one of the world's most important central banks, heading a system with a combined balance sheet of close to €7 trillion.

The ECB Governing Council makes monetary policy for the Eurozone and the European Union, administers the foreign exchange reserves of EU member states, engages in foreign exchange operations, and defines the intermediate monetary objectives and key interest rate of the EU. The ECB Executive Board enforces the policies and decisions of the Governing Council, and may direct the national central banks when doing so. The ECB has the exclusive right to authorise the issuance of euro banknotes. Member states can issue euro coins, but the volume must be approved by the ECB beforehand.

The bank also operates the T2 payments system.

The ECB was established by the Treaty of Amsterdam in May 1999 with the purpose of guaranteeing and maintaining price stability. On 1 December 2009, the Treaty of Lisbon became effective and the bank gained the official status of an EU institution. When the ECB was created, it covered a Eurozone of eleven members. Since then, Greece joined in January 2001, Slovenia in January 2007, Cyprus and Malta in January 2008, Slovakia in January 2009, Estonia in January 2011, Latvia in January 2014, Lithuania in January 2015, Croatia in January 2023, and Bulgaria in January 2026.

The current president of the ECB is Christine Lagarde. Seated in Frankfurt, Germany, the bank formerly occupied the Eurotower prior to the construction of its new seat.

The European Central Bank is the de facto successor of the European Monetary Institute (EMI). The EMI was established at the start of the second stage of the EU's Economic and Monetary Union (EMU) to handle the transitional issues of states adopting the euro and prepare for the creation of the ECB and European System of Central Banks (ESCB). The EMI itself took over from the earlier European Monetary Cooperation Fund (EMCF).

The ECB formally replaced the EMI on 1 June 1998 by virtue of the Treaty on European Union (TEU, Treaty of Maastricht), however it did not exercise its full powers until the introduction of the euro on 1 January 1999, signalling the third stage of EMU. The bank was the final institution needed for EMU, as outlined by the EMU reports of Pierre Werner and President Jacques Delors. It was established on 1 June 1998 The first President of the Bank was Wim Duisenberg, the former president of the Dutch central bank and the European Monetary Institute.

While Duisenberg had been the head of the EMI (taking over from Alexandre Lamfalussy of Belgium) just before the ECB came into existence, the French government wanted Jean-Claude Trichet, former head of the French central bank, to be the ECB's first president. The French argued that since the ECB was to be located in Germany, its president should be French. This was opposed by the German, Dutch and Belgian governments who saw Duisenberg as a guarantor of a strong euro.

Tensions were abated by a gentleman's agreement in which Duisenberg would stand down before the end of his mandate, to be replaced by Trichet.

Trichet replaced Duisenberg as president in November 2003. Until 2007, the ECB had very successfully managed to maintain inflation close but below 2%.

The European Central Bank underwent through a deep internal transformation as it faced the 2008 financial crisis and the Euro area crisis.

The Euro area crisis began after Greece's new elected government uncovered the real level of indebtedness and budget deficit and warned EU institutions of the imminent danger of a Greek sovereign default.

Foreseeing a possible sovereign default in the eurozone, the general public, international and European institutions, and the financial community reassessed the economic situation and creditworthiness of some Eurozone member states. Consequently, sovereign bonds yields of several Eurozone countries started to rise sharply. This provoked a self-fulfilling panic on financial markets: the more Greek bonds yields rose, the more likely a default became possible, the more bond yields increased in turn.

This panic was also aggravated because of the reluctance of the ECB to react and intervene on sovereign bond markets for two reasons. First, because the ECB's legal framework normally forbids the purchase of sovereign bonds in the primary market (Article 123. TFEU), An over-interpretation of this limitation inhibited the ECB from implementing quantitative easing like the Federal Reserve and the Bank of England did as soon as 2008, which played an important role in stabilizing markets.

In a remarkable U-turn, the ECB announced on 10 May 2010 the launch of a "Securities Market Programme" (SMP) which involved the discretionary purchase of sovereign bonds in secondary markets. Extraordinarily, the decision was taken by the Governing Council during a teleconference call only three days after the ECB's usual meeting of 6 May (when Trichet still denied the possibility of purchasing sovereign bonds). The ECB justified this decision by the necessity to "address severe tensions in financial markets".

The decision also coincided with the EU leaders' decision of 10 May to establish the European Financial Stabilisation mechanism, which would serve as a crisis fighting fund to safeguard the euro area from a future sovereign debt crisis.

Although at first limited to the debt of Greece, Ireland and Portugal, the bulk of the ECB's bond buying eventually consisted of Spanish and Italian debt. These purchases were intended to dampen international speculation against stressed countries, and thus avoid a contagion of the Greek crisis towards other Eurozone countries. The assumption—largely justified—was that speculative activity would decrease over time and the value of the assets increase.

Although SMP purchases did inject liquidity into financial markets, all of these injections were "sterilized" through weekly liquidity absorption. So the operation was net neutral in liquidity terms (though this was of little practical importance since normal monetary policy operations were ensuring unlimited supplies of liquidity at the main policy interest rate).