Offenbach am Main is a city in Hesse, Germany, on the left bank of the river Main. It borders Frankfurt and is part of the Frankfurt urban area and the larger Frankfurt Rhein-Main urban area. It has a population of 138,335.

The Main is the longest tributary of the Rhine. It rises as the White Main in the Fichtel Mountains of northeastern Bavaria and flows west through central Germany for 525 kilometres (326 mi) to meet the Rhine below Rüsselsheim, Hesse. The cities of Mainz and Wiesbaden are close to the confluence.