The Kat River (Afrikaans: Katrivier) is a tributary of the Great Fish River, that drains the southern slopes of the Winterberg in the Eastern Cape Province, South Africa.

Kat, meaning "cat", is a translation of the Khoekhoen word "huncu", that apparently referred to the wildcats of the area. It lent its name to Katberg, the Katberg Pass and the Kat River Settlement.

The 150 kilometres (93 mi) long Kat River rises 30 km north of Fort Beaufort in the Katberg escarpment of the Winterberg. At 32°59′44″S 26°47′5″E / 32.99556°S 26.78472°E / -32.99556; 26.78472 it forms a northern tributary of the Great Fish River, northeast of Fort Brown and south of Hamburg, Eastern Cape.

It supplies the Kat River Valley with irrigation water for large citrus orchards, and supplies Seymour and Fort Beaufort with domestic water.

Dams

• Katrivier Dam

• List of rivers in South Africa