The Roper River is a "large, perennial flowing river and has a catchment area of 81,794 km2, which is one of the largest river catchment areas in the Katherine region". The Roper River starts as Roper Creek (also called Little Roper River) and becomes the Roper River downstream of Waterhouse River junction near Mataranka. It is navigable for about 145 km, until the tidal limit at Roper Bar, and forms the southern boundary of the region known as Arnhem Land. Mataranka Hot Springs and the township of Mataranka lie close to the river at its western end. Port Roper lies near its mouth on Limmen Bight.
The first European to explore the Roper River was Ludwig Leichhardt in 1845 as he made his way from Moreton Bay to Port Essington. Leichhardt crossed the river at Roper Bar, a rocky shelf which conveniently lies at the high tide limit on the river. He named the river after John Roper, a member of the expedition.
^ ab"Overview of the Roper River Catchment"(PDF). Roper River Catchment: An Assessment of the Physical and Ecological Condition of the Roper River and its Major Tributaries. Northern Territory Government, Department of Land Resource Management. Jan 2001. Retrieved 1 May 2015.