| Cox River | |
| Pushpin Map: | New Zealand#New Zealand South Island |
| Pushpin Map Size: | 270px |
| Pushpin Map Caption: | Mouth of the Cox River |
| Source1 Coordinates: | -42.7448°N 171.907°W |
| Source1 Elevation: | 1250m (4,100feet) |
| Mouth Location: | Poulter River |
| Mouth Elevation: | 540m (1,770feet) |
| Mouth Coordinates: | -42.9007°N 171.9668°W |
| Subdivision Type1: | Country |
| Subdivision Name1: | New Zealand |
| Length: | 29km (18miles) |
| Progression: | Cox River → Poulter River East Branch → Poulter River → Waimakariri River → Pegasus Bay → Pacific Ocean |
| Tributaries Left: | Ellis Stream, Cochran Stream |
| Tributaries Right: | Montgomery Stream, Row Stream, Beckett Stream |
Cox River is a river of the Canterbury region of New Zealand. It arises in the Crawford Range of the Southern Alps and flows generally southward through the Arthur's Pass National Park to join the Poulter River.[1] The river was named for J. W. M. Cox, a landholder in the 1860s at the junction of Cox River and Bull Creek.[2]
Prior to glaciation the Cox River flowed through the Pūkio Stream valley, discharging into the Esk River, a lower tributary of the Waimakariri River. This route was later blocked by a series of terminal moraines deposited by the Cox glacier during the Pleistocene period. The river then created a new outlet through to the main Poulter valley via a rocky gorge, known as McArthur Gorge, which now contains the East Branch of the Poulter.[3]