The Yser River is a river located in northwestern Belgium. It flows through the Flemish Region and is approximately 78 kilometers long. The river originates near the town of Ypres and eventually empties into the North Sea at Nieuwpoort. The Yser is known for its historical significance, particularly during World War I. The river's basin is characterized by flat landscapes and wetlands, making it an important ecological area. The Yser also serves as a natural boundary and has been a site for various military operations throughout history. Its surrounding areas are popular for outdoor activities like hiking and birdwatching.