With 764,104 inhabitants, Frankfurt am Main is the largest city in Hesse and the fifth largest in Germany. It is district-free and forms the centre of the Frankfurt conurbation with more than 2.3 million inhabitants. Around 5.8 million people live in the Frankfurt/Rhine-Main metropolitan region.

Since the Middle Ages, Frankfurt am Main has been one of the most important urban centres in Germany. First mentioned in a document in 794, it was an imperial city from 1372. Until the end of the Holy Roman Empire in 1806, most of the Roman-German kings were elected in Frankfurt am Main and from 1562 onwards they were also crowned emperor. From 1815 onwards, the Free City of Frankfurt was a sovereign member state of the German Confederation and also its political centre. It was the seat of the Federal Assembly and, in 1848/49, of the National Assembly and the Provisional Central Authority.

After the German War of 1866, Prussia annexed the Free City of Frankfurt. Rapid industrialisation triggered a population surge. Since 1875 the city has had over 100,000 inhabitants, and since 1928 more than 500,000. As a sign of its commitment to European unification, Frankfurt has called itself a European city since 1998.