The main advantage of the American economy, the source of its financial dominance, is the special role of the national currency, i.e., the US dollar (USD$) in international trade and finance, as a unit of account, store of value and medium of exchange on a global scale. As a currency, the dollar derives its value from a combination of factors, primarily the fundamental principle of supply and demand. The dollar is also influenced by interest rates and the overall health and performance of the US economy. Gross domestic product (GDP), employment levels, inflation rates, monetary and fiscal policy, political stability and geopolitical events directly affect market sentiment and investor confidence, which ultimately affects the value of the currency. This can also be seen in the changes in exchange rates, the US dollar index (USDX) and purchasing power parity (PPP). The aim of this paper is to determine the importance of the dollar as a world currency and to analyse how the dollar became a world currency, how it achieves its value and what its overall value is to the American economy based on the factors mentioned. The thesis analyses the status of the dollar as the most influential currency of the twentieth and twenty-first century using data from the literature, academic articles and available databases thematically related to the research objective. In order to obtain relevant data, a comparative analysis of the American dollar (USD) with the euro (EUR),the Japanese yen (JPY), the British pound (GBP), the Chinese renminbi (CNY) and other currencies was primarily conducted. The results of the analysis show that the dollar today enjoys the status of the most important world currency, as it is included in more than 50 % of the world's trade invoices and even around 88 % of the world's foreign exchange turnover, while its share in total foreign currency debt is over 60 % and its share in foreign exchange reserves is around 57 % of all currencies.