The Sepik River is located on which large island?

The Sepik River is the longest river on the island of New Guinea, and after the Fly and the Mamberamo, the third largest by volume. The majority of the river flows through the Papua New Guinea (PNG) provinces of Sandaun (formerly West Sepik) and East Sepik, with a small section flowing through the Indonesian province of Papua.

New Guinea is a large island separated by the shallow Torres Strait from the rest of the Australian continent. It is the world's second-largest island, after Greenland, covering a land area of 785,753 km2 (303,381 sq mi), and the largest island wholly or partly within the Southern Hemisphere and Oceania.

The eastern half of the island is the major land mass of the independent state of Papua New Guinea. The western half, known as Western New Guinea or West Papua, forms a part of Indonesia and comprises the provinces of Papua and West Papua.

The Sepik has a large catchment area, and landforms that include swamplands, tropical rainforests and mountains. Biologically, the river system is often said to be possibly the largest uncontaminated freshwater wetland system in the Asia-Pacific region.

The word 'Sipik' was first reported by A. Full as one of two names for the watercourse—the other being 'Abschima'—used by the natives living at the mouth of the river. A few years later, German explorer, zoologist, and anthropologist, Leonhard Schultze applied the term 'Sepik' to the entire watercourse, and it took.