Sepik may refer to places in Papua New Guinea:
- Sepik River
- East Sepik - a province
- Sandaun - a province formerly known as West Sepik
- Sepik region - consisting of East Sepik and Sandaun provinces
In languages it may refer to:
- Sepik languages - a proposed language family
The Sepik River (was named Kaiserin Augusta River, after the German Empress Augusta by the German colonial explorer Otto Finsch) 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 and East Sepik, with a small section flowing through the Indonesian province of Papua.
The Sepik has a large catchment area and landforms that include swamplands, tropical rainforests and mountains. Biologically, the river system is possibly the largest uncontaminated freshwater wetland system in the Asia-Pacific region.