Knokke-Heist is a municipality in the Belgian province of West Flanders. The municipality comprises the towns of Heist-aan-Zee, Knokke, Duinbergen, Ramskapelle and Westkapelle. On January 1, 2006 Knokke-Heist had a total population of 34,063. Knokke-Heist is located along the North Sea in a polder area on the Belgian border with the Netherlands. It is Belgium's best-known and most affluent seaside resort.

Originally, the marshy Zwin area was mostly settled by shepherds and fishermen. With the encouragement of the Counts of Flanders, several dikes were built between the 11th and the 13th century and the land successfully dewatered, giving rise to agriculture and further sheep breeding. New parishes were founded and the early settlement of Sint-Anna-ter-Muiden, later made part of Westkapelle, obtained city rights in 1242.

The strategic importance of the Zwin harbour was recognized in 1301, during the war between Count Guy of Dampierre and the French King Philip the Fair. During the Hundred Years' War that followed shortly after, several battles were fought between France and England for supremacy of the area including the Battle of Sluys in June 1340. The local population tried to remain neutral as it was politically tied to Flanders, then allied to France, but economically dependent on wool from England. Under Philip the Bold's leadership, it took advantage of the relative peace of the end of the century to fortify the canal linking the Zwin to the port of Bruges.