William, Landgrave of Hesse-Rotenburg

After his father's death in 1693, William ruled one half of the Rotenburg Quarter, the quarter of Hesse-Kassel which Landgrave Maurice of Hesse-Kassel had distributed as fiefs among the sons of his second wife, Juliane. He officially resided in Rotenburg an der Fulda, but he often stayed in Langenschwalbach in the Taunus area. His descendants ruled the Rotenburg Quarter; his grandson, Constantine reunited all the parts of the Quarter.

William's dominions included the lower part of the County of Katzenelnbogen and the districts and castles of Burg Rheinfels, Reichenberg and Hohenstein as well as shares of Umstadt and Vierherren an der Lahn. He swapped the district and city of Eschwege with his brother Charles for the district and city of Rotenburg. He also held the dominions of Falkenberg, Cornberg and Langenschwalbach and he received a share of the Hessian toll on the Rhine and custom duties on wine, agriculture and wool and the toll at Boppard.

William died in 1725 and was buried in the Catholic Church of St. Elizabeth in Langenschwalbach.

William married on 3 March 1669 in Rochefort Countess Maria Anna of Löwenstein-Wertheim (1652–1688). Anna died in 1688 and was buried in the Franciscan monastery in Boppard. With her, he had eight children, including his successor, Ernest II Leopold:

• Eleonore (born: November 26, 1674)
• Eleonore Maria Amalia (born: 25 September 1675) married Eustace Theodore, Count Palatine of Sulzbach
• Elisabeth Catherine Felicitas (born: 14 February 1677) married firstly Francis Alexander, Prince of Nassau-Hadamar; married secondly Count Anton Ferdinand of Attems
• Sophie (born: 4 April 1678)
• Maria Amelie Wilhelmine (born: August 6, 1679)
• Johanna (born: 12 September 1680), abbess
• Ernestine (born: 23 October 1681) married Roberto, Conde de la Cerda de Villalonga
• Ernest II Leopold (born: 25 June 1684), Landgrave of Hesse-Rotenburg married Eleonore Maria Anna, Countess of Löwenstein-Wertheim-Rochefort