Castries District is one of 10 districts of the Caribbean island nation of Saint Lucia. According to the 2012 census, the population of the district was 80,573, having shown a slow but steady increase over the past ten years. The capital of Saint Lucia, the city of Castries, is located in this district. During the Saint Lucia Jazz Festival, the city of Castries plays host to several stages.

Saint Lucia is an island country of the West Indies in the eastern Caribbean. The island was previously called Iouanalao and later Hewanorra, names given by the native Arawaks and Caribs (respectively), two Amerindian peoples. Part of the Windward Islands of the Lesser Antilles, it is located north/northeast of the island of Saint Vincent, northwest of Barbados and south of Martinique. It covers a land area of 617 km2 with an estimated population of over 180,000 people as of 2018. The nation's capital and largest city is Castries.