The Battle of Saint Cast was a military engagement during the Seven Years' War on the French coast between British naval and land expeditionary forces and French coastal defence forces. Fought on 11 September 1758, it was won by the French. During the Seven Years' War, Britain mounted numerous amphibious expeditions against France and French possessions around the world. In 1758 a number of expeditions, then called Descents, were made against the northern coast of France. The military objectives of the descents were to capture and destroy French ports, divert French land forces from Germany, and suppress privateers operating from the French coast. The battle of Saint Cast was the final engagement of a descent in force that ended in a French victory.

While the British continued such expeditions against French colonies and islands beyond the reach of the French land forces, this was the last attempt by an amphibious expedition in force against the coast of France during the Seven Years' War. The fiasco of the embarcation from Saint Cast helped convince British Prime Minister Pitt to send instead military aid and troops to fight alongside Ferdinand and Frederick the Great on the continent of Europe. The negative potential for another disaster and expense of expeditions this size was considered to outweigh the temporary gain of the raids.