The Waitahu River is the largest tributary of the Inangahua River, located approximately 4.5km north of Reefton on New Zealand's West Coast. It joins the Inangahua from the right bank, with road access available along Gannons Road off State Highway 69. A 4WD vehicle is advisable beyond the bridge at the end of the tar seal, where a track follows the true right bank upstream for 9 to 10 kilometres.

For paddlers, the river offers a short trip on a braided shingle channel with a slight average gradient, making it suitable for canoeists and small rafts. Road access reaches approximately 8km above the confluence with the Inangahua, providing a convenient put-in point for a downstream run. The character of the river is that of a typical West Coast braided shingle waterway, with the trip described as short in overall length.

Water clarity during summer is notably high, which is worth considering for paddlers who may also be sharing the river with anglers spotting and stalking trout. The Waitahu holds fish throughout its length, and the Montgomerie, a mid-sized tributary, joins it further upstream. Paddlers should be aware that the river sees use from fly fishers, particularly as the season progresses. The setting is described as particularly scenic.