It is a tributary of the Riet River[1] that forms part of the border between the Northern Cape and the Free State provinces.

The river's banks were the scenes of heavy fighting in the beginning of the Second Boer War at the Battle of Modder River.

[2][3] The Modder River is used extensively for irrigation, including the Krugersdrift Dam near Bloemfontein.

Media related to Modder River at Wikimedia Commons

This article related to a river in South Africa is a stub.