William IV, Grand Duke of Luxembourg
|Reign||17 November 1905 – 25 February 1912|
|Spouse||Infanta Marie Anne of Portugal|
|Marie-Adélaïde, Grand Duchess of Luxembourg
Charlotte, Grand Duchess of Luxembourg
Hilda, Princess of Schwarzenberg
Antoinette, Crown Princess of Bavaria
Elisabeth, Princess Ludwig Philipp of Thurn and Taxis
Sophie, Princess Ernst Heinrich of Saxony
|House||House of Nassau-Weilburg|
|Father||Adolphe, Grand Duke of Luxembourg, Duke of Nassau|
|Mother||Princess Adelheid-Marie of Anhalt-Dessau|
22 April 1852|
Biebrich Palace, Wiesbaden
|Died||25 February 1912
Berg Castle, Colmar-Berg
|Burial||Schlosskirche (“Castle Church”) in Weilburg since 1953|
William IV, Grand Duke of Luxembourg (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 titular title of Duke of Nassau.
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 heiress-presumptive to the grand ducal throne. She became Luxembourg's first reigning female monarch 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 have reigned until the present day.
He was the last monarch of Luxembourg to die in office.
On 21 June 1893 in Fischhorn Castle, Zell am See, he married Infanta Marie Anne of Portugal, daughter of the deposed king Miguel I of Portugal and Adelaide of Löwenstein-Wertheim-Rosenberg. The couple had six daughters, but no sons:
- 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 (Berg Castle, 15 February 1897 – Berg Castle, 8 September 1979), married in Berg Castle on 29 October 1930 Adolf 10th Prince of Schwarzenberg (Frauenberg, 18 August 1890 – Bordighera, 27 February 1950), without issue
- Princess Antonia (1899–1954), who married Crown Prince Rupprecht of Bavaria as his second wife
- Princess Elisabeth (Luxembourg, 7 March 1901 – Schloss Hohenburg, 2 August 1950), married in Schloss Hohenburg on 14 November 1922 Prince Ludwig Philipp of Thurn and Taxis (Regensburg, 2 February 1901 – Schloss Niederaichbach, 22 April 1933), son of Albert I, Prince of Thurn and Taxis, and had issue
- Princess Sophie (Berg Castle, 14 February 1902 – Munich, 24 May 1941), married at Schloss Hohenburg on 12 April 1921 Prince Ernst Heinrich of Saxony (Dresden, 9 December 1896 – Neckarhausen, 14 June 1971), youngest son of king Frederick Augustus III of Saxony, and had issue
Titles an styles 
- 22 April 1852 – 20 September 1866: His Highness The Hereditary Prince of Nassau
- 20 September 1866 – 23 November 1890: His Highness Prince Wilhelm Alexander of Nassau
- 23 November 1890 – 17 November 1905: His Royal Highness The Hereditary Grand Duke of Luxembourg, Prince of Nassau
- 17 November 1905 – 25 February 1912: His Royal Highness The Grand Duke of Luxembourg
- Almanach de Gotha (1901), article "Luxembourg"
- http://pages.prodigy.net/ptheroff/gotha/schwarzenberg.html Princely House of Schwarzenberg
- http://pages.prodigy.net/ptheroff/gotha/thurn.html Princely House of Thurn and Taxis
- http://pages.prodigy.net/ptheroff/gotha/saxony.html Royal House of Saxony
- Members of the German Ducal Houses uses the style of Highness
- It was customary for a reigning Grand Duke, his heir apparent, and their spouses to use the style of Royal Highness
- Miroslav MAREK. "Hesse-Homburg", 2003-05-02. Retrieved on 2009-03-05
William IV, Grand Duke of LuxembourgBorn: 12 April 1852 Died: 25 February 1912
|Grand Duke of Luxembourg
|Titles in pretence|
|— TITULAR —
Duke of Nassau
Reason for succession failure:
Duchy annexed by Prussia in 1866