Friedrich Wilhelm Paul Leopold (4 January 1785; Lindenau, Prussia - 17 February 1831; Gottorp, Schleswig, Duchy of Schleswig) was the first Duke of the Second Line of Schleswig-Holstein-Sonderburg-Glücksburg and founder of a line that includes the Royal Houses of Denmark, Greece, Norway, and the United Kingdom. Friedrich Wilhelm is a grandfather to Alexandra of Denmark, and subsequently is an ancestor to the present-day British Royal Family, including Elizabeth II of the United Kingdom and her husband, Prince Philip, Duke of Edinburgh.