This thesis is a comprehensive analysis of the European Central Bank, the most important financial institution in the European Union. First of all, a detailed analysis of historical facts describing the beginnings and stages of development of monetary union in Europe provides insight into the original goals of monetary union, which in the development cycle led to the final establishment of the European Central Bank, as we know it today. The European Central Bank is the central bank of 19 European Union member states whose currency is the euro, and its main task is to maintain price stability. In order to successfully carry out its tasks, and thus to improve the functioning of the entire monetary union, the institution of the European Central Bank has the power to adopt legal acts and give opinions on proposed legislation in its areas of competence. Furthermore, its role as an institution of the European Union was greatly highlighted from the onset of the financial crisis in mid-2007 because it contributed to maintaining stability and restoring confidence in the European financial system by adopting new measures. On 10 July 2020, the Republic of Croatia was admitted to the European Exchange Rate Mechanism II, which confirmed its fulfillment of the Eurozone targets, and in the same year the Plan for the Exchange of Kuna with the Euro was adopted. After January 1, 2023 and the official introduction of the euro, the Republic of Croatia, through the Croatian National Bank as its central bank, will finally become equal in decision-making and in the most important European financial institution, the European Central Bank.