The Mangaehu Stream is a 55-kilometer waterway located in the Taranaki region of New Zealand's North Island. It is a tributary of the Pātea River, into which it flows. The stream's character is defined by its role within the larger Pātea River system, which is noted as the only navigable river in South Taranaki, suggesting the Mangaehu may offer connected paddling opportunities. The Pātea River system originates on the eastern slopes of Mount Taranaki and progresses to the South Taranaki Bight of the Tasman Sea. A significant feature of this river system is Lake Rotorangi, a 46-kilometer-long man-made lake created by the Pātea Dam, which may be relevant for paddlers exploring the wider watershed. The area holds historical significance as the Pātea River was an early portal to South Taranaki for both Māori and European settlers. Paddlers should note that the stream is in a region with active fishing, as indicated by community fishing reports.