The siege of Rees of 1599, also known as the relief of Rees (Socorro de Rees in Spanish), was an unsuccessful attempt by Protestant-German forces led by Count Simon VI of Lippe, and Anglo-Dutch forces sent by Prince Maurice of Nassau (Dutch: Maurits van Oranje), commanded by Philip of Hohenlohe-Neuenstein and the , to capture the strategic stronghold of Rees, Lower Rhine, Duchy of Cleves (present-day Germany) from the Spanish forces of Don Francisco de Mendoza, Admiral of Aragon, second-in-command of the Army of Flanders, and Governor Don , between 10–12 September 1599, during the Eighty Years' War and the Anglo-Spanish War (1585–1604). This Spanish victory was part of the campaign of Francisco de Mendoza and Cardinal Andrew of Austria of 1598-1599, also called the Spanish Winter of 1598-9