| Mathias River | |
| Source1 Location: | Southern Alps |
| Mouth Location: | Rakaia River |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Length: | 170NaN0 |
The Mathias River is a river of the Canterbury region of New Zealand's South Island. It flows from its origins in three rivers (the North, South, and West Mathias Rivers) in the Southern Alps. Of these, the North Mathias River is the longest, flowing predominantly southwards from its source northeast of Mount Williams. After 18km (11miles) its waters combine with those of the West Mathias River, which flows predominantly southwest for 13km (08miles) from its sources 10km (10miles) west of Mount Williams. The South Mathias River, a tributary of the West Mathias River, is a 60NaN0 long easterly-flowing river which meets the West Mathias 5km (03miles) from its confluence with the North Mathias.
The combined waters flow a further 17km (11miles) southeast across a braided, shingle strath, which meets with the valley of the Rakaia River 15km (09miles) west of Lake Coleridge.
The river was named by Sir Julius von Haast after his companion Alured George Mathias, during his Rakaia trip.[1]