Frankfurt am Main, usually shortened to Frankfurt, is the most populous city in the German state of Hesse. Its 778,589 inhabitants as of 2025 make it the fifth-most populous city in Germany. Located in the foreland of the Taunus on its namesake Main, the city forms a continuous conurbation with Offenbach am Main; its urban area has a population of over 2.7 million. Frankfurt is the heart of the larger Rhine-Main metropolitan region, which has a population of more than 5.8 million and is Germany's second-largest metropolitan region after the Rhine-Ruhr region. Home to the European Central Bank, the city serves as one of the four institutional seats of the European Union (alongside Brussels, Luxembourg, and Strasbourg). Frankfurt is classified by the GaWC as an Alpha-rated world city.