Ourthe

The Ourthe is a river in eastern Belgium and a right-bank tributary of the Meuse. It is formed by the confluence of two headwaters, the Ourthe Orientale and Ourthe Occidentale, in the Ardennes. The river flows generally northwest for roughly 160–170 kilometers through the provinces of Luxembourg and Liège, passing towns such as Houffalize, La Roche-en-Ardenne, and Durbuy, and it finally joins the Meuse near Liège.

The flow regime is temperate, with higher discharge in winter and spring and lower levels in summer. The upper Ourthe flows through forested gorges and limestone valleys; the middle and lower Ourthe traverse farmland and small towns. Water quality has improved since the late 20th century thanks to wastewater improvements and river restoration projects. The Ourthe is part of the natural habitat network and supports diverse aquatic life, including brown trout in the upper reaches and other freshwater species along its course.

The valley has been inhabited since prehistoric times; in the Middle Ages, the river powered mills and small industries; today it is a popular destination for tourism and outdoor recreation.

The Ourthe basin includes protected areas and is part of the Natura 2000 network in Belgium, aimed at preserving habitats for fish, amphibians, and birds.

The name Ourthe is of uncertain origin, likely from a pre-Roman river name of Celtic or Gaulish origin.