Friedrich Wilhelm, Duke of Schleswig-Holstein-Sonderburg-Glücksburg

Friedrich Wilhelm, Duke of Schleswig-Holstein-Sonderburg-Glücksburg (German: Friedrich Wilhelm Paul Leopold; Danish: Frederik Vilhelm Paul Leopold; 4 January 1785 – 17 February 1831) was a German-Danish prince and officer who was the Duke of Schleswig-Holstein-Sonderburg-Beck from 1816 to 1825, and the Duke of Schleswig-Holstein-Sonderburg-Glücksburg from 1825 to 1831. Friedrich Wilhelm is the progenitor of the House of Glücksburg.

Friedrich Wilhelm was the only son of Friedrich Karl Ludwig, Duke of Schleswig-Holstein-Sonderburg-Beck and Countess Friederike of Schlieben, and was a member of the ducal house of Schleswig-Holstein-Sonderburg-Beck, a junior male branch of the House of Oldenburg. From 1804, he lived in his family's original home in Denmark-Norway, where he made a career as an officer of the Danish army during the Napoleonic Wars. His 1810 marriage to Princess Louise Caroline of Hesse-Kassel meant that Friedrich Wilhelm became brother-in-law to King Frederick VI of Denmark, as his wife's elder sister was married to the king. At the death of his father in 1816, he inherited the title of Duke of Schleswig-Holstein-Sonderburg-Beck as Frederick William IV, and in 1825, upon the extinciton of the elder Glücksburg line in 1824, King Frederick VI transferred Glücksburg Castle to his brother-in-law and changed his title to Duke of Schleswig-Holstein-Sonderburg-Glücksburg.

Duke Friedrich Wilhelm and Duchess Louise Caroline had ten children, of which his eldest son Karl succeeded him as Duke of Glücksburg, and his fourth son became King of Denmark in 1863 as King Christian IX.