The Lys or Leie is a river in France and Belgium, and a left-bank tributary of the Scheldt. Its source is in Pas-de-Calais, France, and it flows into the river Scheldt in Ghent, Belgium. Its total length is 202 kilometres.
Historically a very polluted river from the high population density and industrialisation in both Northern France and Belgium, it has seen substantial improvements in recent years, partly due to the decline of the principal industry, the spinning and weaving of flax. The region of the Leie was known as a favourite place for numerous painters in the first half of the 20th century.
The source of the Lys is in a village, Lisbourg, east of Fruges, in the Pas-de-Calais department of France. It flows generally northeast through the following departments of France, provinces of Belgium and towns and municipalities:
Pas-de-Calais: Thérouanne, Aire-sur-la-Lys
Nord: Merville, Armentières, Halluin
Hainaut: Comines-Warneton
West Flanders: Menen, Wevelgem, Kortrijk, Waregem, Wervik
East Flanders: Zulte, Deinze, Ghent
The main tributaries of the Leie are, from source to mouth: Laquette, Clarence, Lawe, Deûle, Gaverbeek, Heulebeek, and Mandel.