William II, 1626–50, prince of Orange, stadtholder of the United Provinces of the Netherlands (1647–50), son and successor of Frederick Henry. He married (1641) Mary, eldest daughter of Charles I of England. His ambitious projects brought him into conflict with the great merchants of Amsterdam. He opposed acceptance of the Treaty of Münster (1648), despite its recognition of the independence of the Netherlands, and he immediately began secret negotiations with France, having as his purpose the extension of his territory, the centralization of his government, and the restoration of his brother-in-law, Charles II, to the English throne. The prompt resistance he encountered from the states of Holland was not broken by William's imprisonment of its leaders (1650). He next turned his attention to external affairs and was negotiating a treaty with France when he died of smallpox. He was succeeded by his posthumous son, the future William III of England.