|Intro||Grand Duke of Luxembourg|
|A.K.A.||Guillaume IV, Wilhelm IV|
|Birth||22 April 1852 (Biebrich Palace, Hesse, Germany)|
|Death||25 February 1912 (Berg Castle, Colmar-Berg, Canton of Mersch, Luxembourg District)|
William IV (22 April 1852 – 25 February 1912) reigned as the sovereign Grand Duke of Luxembourg from 17 November 1905 until his death. He succeeded his father, Adolphe, Grand Duke of Luxembourg. He also held the title of Duke of Nassau, although that was annexed by Prussia after the Austro-Prussian war of 1866.
William IV was a Protestant, the religion of the House of Nassau. He married Princess Marie Anne of Portugal, believing that a Roman Catholic country ought to have a Roman Catholic monarch. Thus since William IV all other Grand Dukes have been Catholic.
At the death of his uncle, Prince Nikolaus-Wilhelm in 1905, the only other legitimate male in the House of Nassau-Weilburg was William's cousin, Georg Nikolaus, Count of Merenberg, the product of a morganatic marriage. So in 1907, William declared the Counts of Merenberg non-dynastic, naming his own eldest daughter Marie-Adélaïde (1894–1924) as heir presumptive to the grand ducal throne. She became Luxembourg's first reigning grand duchess upon her father's death in 1912, and upon her own abdication in 1919, was succeeded by her younger sister Charlotte (1896–1985). Charlotte's descendants reign until the present day.
He was the last monarch of Luxembourg to die whilst still on the throne.
On 21 June 1893 in Fischhorn Castle, Zell am See, he married Infanta Marie Anne of Portugal, daughter of the Usurper Miguel of Portugal and Adelaide of Löwenstein-Wertheim-Rosenberg. The couple had six daughters:
- Marie-Adélaïde, Grand Duchess of Luxembourg (1894–1924) who remained unmarried and childless
- Charlotte, Grand Duchess of Luxembourg (1896–1985) who married her first cousin Prince Felix of Bourbon-Parma, a son of Marie Anne's younger sister.
- Princess Hilda (15 February 1897 in Berg Castle – 8 September 1979 in Berg Castle), married in Berg Castle on 29 October 1930 Adolf 10th Prince of Schwarzenberg (18 August 1890 in Frauenberg – 27 February 1950 in Bordighera), without issue
- Crown Princess Antonia of Bavaria (1899–1954), who married Crown Prince Rupprecht of Bavaria as his second wife
- Princess Elisabeth (7 March 1901 in Luxembourg – 2 August 1950 in Schloss Hohenburg), married in Schloss Hohenburg on 14 November 1922 Prince Ludwig Philipp of Thurn and Taxis (2 February 1901 in Regensburg – 22 April 1933 in Schloss Niederaichbach), son of Albert I, Prince of Thurn and Taxis, and had issue
- Princess Sophie (14 February 1902 in Berg Castle – 24 May 1941 in Munich), married at Schloss Hohenburg on 12 April 1921 Prince Ernst Heinrich of Saxony (9 December 1896 in Dresden – 14 June 1971 in Neckarhausen), youngest son of king Frederick Augustus III of Saxony, and had issue
Titles and honours
- 22 April 1852 - 23 November 1890: His Highness The Hereditary Prince of Nassau
- 23 November 1890 - 17 November 1905: His Royal Highness The Hereditary Grand Duke of Luxembourg, Hereditary Prince of Nassau
- 17 November 1905 - 25 February 1912: His Royal Highness The Grand Duke of Luxembourg, Duke of Nassau
- Luxembourg: Grand Master and Knight of the Order of the Gold Lion of the House of Nassau
- Luxembourg: Grand Master of the Order of Adolphe of Nassau
- Luxembourg: Grand Master of the Order of the Oak Crown
- Netherlands: Knight Grand Cross of the Order of the Netherlands Lion
|Ancestors of William IV, Grand Duke of Luxembourg|