The Rhenohercynian Zone or Rheno-Hercynian zone in structural geology describes a fold belt of west and central Europe, formed during the Hercynian orogeny (about 350 to 280 million years ago). The zone consists of folded and thrusted Devonian and early Carboniferous sedimentary rocks that were deposited in a back-arc basin along the southern margin of the then existing paleocontinent Laurussia.
The Rhenohercynian Zone, named for the Rhine River and the Hercynian Forest of Antiquity, forms a narrow zone through western and central Europe, from Cornwall and Ireland in the west to the Harz mountains of central Germany in the east, including the Rhenish Massif (Ardennes, Taunus, Eifel and Hunsrück). The total length of this ancient basin (the Rhenohercynian Basin) could have been more than 2500 km. In the east the basin merges with the East-Silesian basin of southern Poland. The sedimentary rocks that were laid down in the basin are often weakly metamorphic (greenschist facies). Most geologists consider the South-Portuguese zone to be a continuation of the zone to the west.