The Lords of Coucy (French: sires de Coucy or seigneurs de Coucy), also spelt Couci, were a medieval lordship based on the barony of Coucy located in the current commune of Coucy-le-Château-Auffrique, Picardy. The château de Coucy was founded by Hervé, archbishop of Rheims, and remained under the fluctuating control of these archbishops for some time until probably the later part of the 10th century. The exact status of Coucy becomes obscure for nearly a century before the emergence of Lord Aubrey, Earl of Northumbria. Though the Lords of Coucy were entitled to the title of baron, they preferred the rarer Sire.
The lords of Coucy became, especially in the 13th century, one of the most powerful sub-comital magnates in western Europe and forged links with royal families, such as those of France, England, Scotland and Austria. The title was eventually absorbed at the end of the 14th century by Louis of Valois, Duke of Orléans.
