Lys is the name of a département of the First French Empire in present Belgium. It is named after the river Lys. It was created on 1 October 1795, when the Southern Netherlands were annexed by France. Before its occupation, its territory was part of the county of Flanders.
- Bruges, cantons: Ardooie, Bruges (5 cantons), Gistel, Ostend, Ruiselede, Tielt and Torhout (2 cantons).
- Kortrijk, cantons: Avelgem, Harelbeke, Ingelmunster, Kortrijk (4 cantons), Menen, Meulebeke, Moorsele, Oostrozebeke and Roeselare.
- Veurne, cantons: Diksmuide, Haringe, Nieuwpoort and Veurne.
- Ypres, cantons: Elverdinge, Hooglede, Mesen, Passendale, Poperinge, Wervik and Ypres (2 cantons).
Its population in 1812 was 491,143, and its area was 366,911 hectares.