The European Central Bank (ECB) is the central bank of the Eurozone, a monetary union of 19 EU member states which employ the euro. Established by the Treaty of Amsterdam, the ECB is one of the world's most important central banks and serves as one of seven institutions of the European Union, being enshrined in the Treaty on European Union (TEU). The bank's capital stock is owned by all 27 central banks of each EU member state. The current President of the ECB is Christine Lagarde. Headquartered in Frankfurt, Germany, the bank formerly occupied the Eurotower prior to the construction of its new seat.