The source of the Wilge River is near the border between Free State and KwaZulu-Natal near Swinburne. The Wilge River ends when it flows into the Vaal Dam.
The Wilge River flows through Swinburne, Harrismith and Frankfort.
Sterkfontein Dam is on the Wilge River. Water in the dam is predominantly pumped from KwaZulu-Natal to help supplement the water supply in Gauteng.
Along its course the Wilge River is joined by the Meul River, Cornelis River and Liebenbergsvlei.