The Maramarua River is in the north-eastern part of the Waikato District of New Zealand. It is formed by the confluence of the Mangatangi River and the Ruaotehuia Stream just north of State Highway 2 between Mangatāwhiri and Maramarua. It flows through the northern part of the Whangamarino Wetland and joins the Whangamarino River shortly before that river flows into the Waikato River.