The Ramu is a river in northern Papua New Guinea. The headwaters of the river are formed in the Kratke Range from where it then travels approximately 640 kilometres (398 mi) north-west to the Bismarck Sea. Along the Ramu's course it receives numerous tributaries from the Bismarck Range to the south and the Finisterre and Adelbert Ranges from the north. During the wet season the Ramu and Sepik Rivers join across the flood plain.
Local villagers have lived along the river for many millennia and the river has formed the basis for food, transport and culture. The area encompassed by the Ramu was part of Kaiser-Wilhelmsland when Germany established German New Guinea in 1884. The Germans were quick to explore their territory and the mouth of the Ramu was discovered in 1886 by Vice-Admiral Freiherr von Schleinitz after returning to Finschhafen from an expedition to the near-by Sepik. Schleinitz called the Ramu, Ottilien after his ship the Ottilie.