William IV of Orange

William IV
Portrait of William IV (1751), attributed to Johann Valentin Tischbein
Stadtholder of the United Provinces
Reign	4 May 1747 – 22 October 1751
Predecessor	William III
Successor	William V
Prince of Orange
Reign	1 September 1711 – 22 October 1751
Predecessor	John William Friso
Successor	William V
Born	1 September 1711 Leeuwarden, Dutch Republic
Died	22 October 1751(1751-10-22) (aged 40) Huis ten Bosch, The Hague, Dutch Republic
Spouse	Anne of Great Britain
Issue Details...	Carolina, Princess of Nassau-Weilburg Princess Anna of Orange-Nassau William V, Prince of Orange
House	Orange-Nassau
Father	John William Friso, Prince of Orange
Mother	Landgravine Marie Louise of Hesse-Kassel

William IV, Prince of Orange-Nassau (Willem Karel Hendrik Friso; 1 September 1711 – 22 October 1751) was the first hereditary Stadtholder of all the United Provinces.

William was born in Leeuwarden, Netherlands, the son of John William Friso, Prince of Orange, head of the Frisian branch of the House of Orange-Nassau, and of his wife Landgravine Marie Louise of Hesse-Kassel (or Hesse-Cassel). He was born six weeks after the death of his father.

William succeeded his father as Stadtholder of Friesland and also, under the regency of his mother until 1731, as Stadtholder of Groningen. In 1722 he was elected Stadtholder of Guelders.

In 1720 William was named the 549th Knight of the Order of the Garter. On 25 March 1734 he married at St. James' Palace Anne, Princess Royal, eldest daughter of King George II of Great Britain and Caroline of Ansbach. William and Anne had five children:

In 1739 William inherited the estates formerly owned by the Nassau-Dillenburg branch of his family, and in 1743 he inherited those formerly owned by the Nassau-Siegen branch of his family.

In April 1747 the French army entered Flanders, threatening the Netherlands, which was weakened by internal division. The Dutch decided that their country needed a single strong executive, and turned to the House of Orange. William and his family moved from Leeuwarden to The Hague. On 4 May 1747, the States General of the Netherlands named William General Stadtholder of all seven of the United Provinces of the Netherlands, and made the position hereditary for the first time. William first met Duke Louis Ernest of Brunswick-Lüneburg in 1747, and two years later appointed him field marshal of the Dutch States Army, which later led to Louis Ernest serving as one of the regents for William's heir.