The Ergolz is the main river in the canton of Basel-Landschaft, Switzerland. It rises on Mount Geisflue in the Faltenjura mountains in the upper region of Basel-Landschaft, on the border with Aargau and Solothurn, and joins the Rhine at Augst. Among the tributaries of the Ergolz are Eibach, Homburgerbach, Diegterbach, Frenke (Anterior and Posterior Frenke), Orisbach, Röserenbach and Violenbach.