Frankfurt am Main, commonly known as Frankfurt, is the largest city in the German state of Hesse and the fifth-largest city in Germany, with a 2011 population of 695,624.The urban area had an estimated population of 2,300,000 in 2010.The city is at the centre of the larger Frankfurt Rhine-Main Metropolitan Region which has a population of 5,600,000 and is Germany's second-largest metropolitan region.