The Mareb River (or Gash River), is a river flowing out of central Eritrea. Its chief importance is defining part of the boundary between Eritrea and Ethiopia, between the point where the Mai Ambassa enters the river at 14°53.6′N 37°54.8′E / 14.8933°N 37.9133°E / 14.8933; 37.9133 to the confluence of the Ba**** with the Mareb at 14°38′N 39°1.3′E / 14.633°N 39.0217°E / 14.633; 39.0217.