The Gamtoos River is a significant waterway in South Africa's Eastern Cape Province, formed by the confluence of the Kouga River and the Groot River, with the Baviaanskloof River serving as a major tributary of the Kouga. The river stretches approximately 645 kilometres (401 miles) and drains a catchment area of roughly 34,635 square kilometres. It flows toward the Indian Ocean, emptying between Port Elizabeth and Jeffreys Bay, where the R102 and N2 bridges cross near its mouth. The river's name is likely derived from a Khoikhoi clan whose name was recorded by early Dutch settlers as "Gamtousch," and it is known in Xhosa as Xelexwa. The lower reaches and estuary near the river mouth offer some of the most productive fishing opportunities, where saltwater and freshwater species intermingle in a dynamic estuarine environment.