The Dillon River of the Marlborough Region of New Zealand rises in the Inland Kaikà Âura Range near Carters Saddle. From its source, it flows south-west for to join with the upper Waiau Toa / Clarence River northeast of Hanmer Springs. The river's course lies largely parallel with that of the Acheron River, which flows to the west. The river was named after the 19th-century settler Constantine Dillon, who owned a sheep run near the Omaka River.