The Kouga River originates near Uniondale, Eastern Cape, South Africa, and flows eastward, where it joins the Groot River to form the Gamtoos just past the Kouga Dam.

Its main tributary is the Baviaanskloof River, which joins its left bank before the dam.

In 1995 specimens of the Cape galaxias (Galaxias zebratus), a South African fish species endemic to the Cape Floristic Region, were found in the Kouga and in the Krom River.

Until then it had been thought that its distribution was restricted to the area between the Keurbooms and the Olifants River.

[4] Although in South Africa this relatively delicate fish is only classified as near threatened, in Australia species of the same genus were driven to extinction by competing salmonids and other introduced species of fish.