The War of the Jülich Succession, also known as the Jülich War or the Jülich-Cleves Succession Crises (German: Jülich-Klevischer Erbfolgestreit), was a war of succession in the United Duchies of Jülich-Cleves-Berg. The first phase of the war lasted between 10 June 1609 and 24 October 1610, with the second phase starting in May 1614 and finally ending on 13 October 1614. At first, the war pitted Catholic Archduke Leopold V against the combined forces of the Protestant claimants, Johann Sigismund, Elector of Brandenburg and Wolfgang Wilhelm of Palatinate-Neuburg, ending in the former's military defeat. The representatives of Brandenburg and Neuburg later entered conflict amongst themselves, partly due to religious conversions, which led to the resumption of hostilities.
The war was further complicated by the involvement of Spain, the Dutch Republic, France, England, and the Protestant Union, making it closely tied to the Eighty Years' War, as well as part of the European wars of religion. It also corresponded to a Protestant uprising in the Free Imperial City of Aachen. It was finally settled by the Treaty of Xanten, whose provisions favored Spain, though the conflict was not fully resolved until later.