William, Landgrave of Hesse-Philippsthal

William of Hesse-Philippsthal (born 29 August 1726 in Philippsthal; died: 8 August 1810, Philippsthal) was a member of the House of Hesse and Landgrave of Hesse-Philippsthal from 1770 until his death.

William was the eldest son of Landgrave Charles I of Hesse-Philippsthal from his marriage to Caroline Christine of Saxe-Eisenach (1699–1743), daughter of Duke John William III of Saxe-Eisenach.He succeeded his father in 1770 as Landgrave of Hesse-Philippsthal.

William served in the Dutch army as General of the Cavalry and Governor of 's-Hertogenbosch.William was also Komtur of the Knights Hospitallers of the Commandry of Łagów.

In 1806, the Landgraviate of Philippsthal was occupied by French troops and annexed to the short-lived Kingdom of Westphalia.William died before his territory could be liberated from the French.

William married on 22 June 1755 in Tournai his cousin Ulrika Eleonora (1732–1795), daughter of Landgrave William of Hesse-Philippsthal-Barchfeld, with whom he had the following children:

• Caroline (1756–1756)
• Charles (1757–1793), lieutenant colonel in the Guard Regiment of Hesse-Kassel

married in 1791 princess Victoria of Anhalt-Bernburg (1772–1817), daughter of Prince Franz Adolph of Anhalt-Bernburg-Schaumburg-Hoym

• William (1758–1760)
• Frederick (1760–1761)
• Juliane (1761–1799)

married in 1780 Count Philip Ernest of Schaumburg-Lippe (1723–1787)

• Frederick (1764–1794) Imperial lieutenant colonel in a Russian Guard Regiment Cuirassiers
• Louis (1766–1816), Landgrave of Hesse-Philippsthal

married in1791 Countess Marie Francisca Berghe of Trips (1771–1805)

• William (1765–1766)
• Ernest Constantine (1771–1849), Landgrave of Hesse-Philippsthal

married firstly in 1796 Princess Louise of Schwarzburg-Rudolstadt (1775–1808)

married secondly in 1812 Princess Caroline of Hesse-Philippsthal (1793–1872)

• Carl Eduard Vehse: Geschichte der deutschen Höfe seit der Reformation, p. 319
• Georg Hassel: Allg. Europäisches Staats u. Address…, p. 247