Langen is a town located in the Hesse region of Germany, situated within the Offenbach district of the Regierungsbezirk Darmstadt. It is positioned geographically between the cities of Darmstadt and Frankfurt am Main and forms part of the Frankfurt Rhein-Main urban area. The town has a population of approximately 39,000 residents.
The municipality serves as an important administrative and scientific hub for the region. It hosts the headquarters of Deutsche Flugsicherung and is home to the Paul-Ehrlich-Institut, which functions as a federal institute responsible for the evaluation and supervision of sera and vaccines in Germany.