Lys (, ) was a department of the French First Republic and French First Empire in present-day Belgium. It was named after the river Lys (Leie). It was created on 1 October 1795, when the Austrian Netherlands and the Prince-Bishopric of Liège were officially annexed by the French Republic. Prior to this annexation, its territory was part of the County of Flanders. Its Chef-lieu was Bruges.
thumb|Lys within the northern French Empire (1811)
The department was subdivided into the following four arrondissements and cantons (as of 1812):||9 February 1804||François Marie Joseph Justin de Viry
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|9 February 1804||12 May 1808||François Bernard de Chauvelin
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|30 November 1810||25 August 1811||Pierre Amédée Vincent Joseph Marie Arborio-Biamino
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|25 August 1811||30 May 1814||Jean François Soult
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General Secretaries
The General Secretary was the deputy to the Prefect.
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|2 March 1800||30 May 1814||Delanghe
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Subprefects of Courtray
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|25 April 1800