The Lange Eugen is a high-rise building in the Gronau district of Bonn that was built from 1966 to 1969 according to plans by the architect Egon Eiermann. It is located near the banks of the Rhine on Hermann-Ehlers-Straße.
Until the German Bundestag moved to Berlin in 1999, the building was the »new parliamentary high-rise« and was the main location for the offices of the members of the German Bundestag. After the renovation was completed, it was occupied by eleven United Nations organizations from April 2006 and is part of the UN campus that opened in July 2006. The Lange Eugen is a listed building and is a stop on the »Path of Democracy« historical trail.