William I (Dutch: Willem I der Nederlanden; 24 August 1772 – 12 December 1843) was a Prince of Orange and the first King of the Netherlands and Grand Duke of Luxembourg. He was the ruler of the Principality of Nassau-Orange-Fulda from 1803 until 1806 and of the Principality of Orange-Nassau in the year 1806 and from 1813 until 1815. In 1813 he proclaimed himself Sovereign Prince of the United Netherlands. He proclaimed himself King of the Netherlands and Duke of Luxembourg on 16 March 1815. In the same year on 9 June William I became also the Grand Duke of Luxembourg and after 1839 he was furthermore the Duke of Limburg. After his abdication in 1840 he styled himself King William Frederick, Count of Nassau. King William I's parents were the last stadtholder William V, Prince of Orange of the Dutch Republic, and his wife Wilhelmina of Prussia. Until 1806, William was formally known as William VI, Prince of Orange-Nassau and between 1806 and 1813 also as Prince of Orange. In Berlin on 1 October 1791, William married his first cousin (Frederica Louisa) Wilhelmina of Prussia, born in Potsdam. She was the daughter of King Frederick William II of Prussia. After Wilhelmina died in 1837, William married Countess Henriette d'Oultremont de Wégimont. Like his younger brother Prince Frederick of Orange-Nassau he was tutored by the Swiss mathematician Leonhard Euler and the Dutch historian Herman Tollius. They were both tutored in the military arts by General Prince Frederick Stamford. After the Patriot revolt had been suppressed in 1787, he in 1788-89 attended the military academy in Brunswick which was considered an excellent military school, together with his brother. In 1790 he visited a number of foreign courts like the one in Nassau and the Prussian capital Berlin, where he first met his future wife. William subsequently studied briefly at the University of Leiden. In 1790 he was appointed a general of infantry in the States Army of which his father was Captain General, and he was made a member of the Council of State of the Netherlands. In November 1791 he took his new bride to The Hague. After the National Convention of the French First Republic had declared war on the stadtholder of the Dutch Republic in February 1793, William was appointed commander-in-chief of the veldleger (mobile army) of the States Army (his father remained the nominal head of the armed forces). As such he commanded the troops that took part in the Flanders Campaign of 1793-95. In May 1794 he had replaced general Kaunitz as commander of the combined Austro-Dutch forces on the instigation of Emperor Francis II who apparently had a high opinion of him. But the French armies proved too strong, and the allied leadership too inept and the allies were defeated. The French first entered Dutch Brabant which they dominated after the Battle of Boxtel. When in the winter of 1794-95 the rivers in the Rhine delta froze over, the French breached the southern Hollandic Water Line and the situation became militarily untenable. In many places Dutch revolutionaries took over the local government. After the Batavian Revolution in Amsterdam on 18 January 1795 the stadtholder decided to flee to Britain, and his sons accompanied him. The next day the Batavian Republic was proclaimed.

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