Wilhelm Friedrich, Duke of Schleswig-Holstein-Sonderburg-Glücksburg, from 1934 Duke of Schleswig-Holstein (in German: Wilhelm Friedrich Christian Günther Albert Adolf Georg Prinz zu Schleswig-Holstein-Sonderburg-Glücksburg then Prinz zu Schleswig-Holstein; 23 August 1891 – 10 February 1965), was the sixth Duke of Schleswig-Holstein and Head of the House of Oldenburg from 21 January 1934 until his death on 10 February 1965.[citation needed]
Prince Friedrich was born on 23 August 1891 at Grünholz Castle in Schleswig-Holstein, Kingdom of Prussia. He was the fifth child and only son of Frederick Ferdinand, Duke of Schleswig-Holstein-Sonderbug-Glücksburg and his wife, Princess Karoline Mathilde of Schleswig-Holstein-Sonderburg-Augustenburg.[citation needed]
Prince Friedrich's father was the eldest son of Friedrich, Duke of Schleswig-Holstein-Sonderburg-Glücksburg and a nephew of Christian IX of Denmark. Upon the death of his father in 1885, he had succeeded to the headship of the House of Schleswig-Holstein-Sonderburg-Glücksburg and the title of duke.[citation needed]
Friedrich married his second cousin, Princess Marie Melita of Hohenlohe-Langenburg, daughter of Ernst II, Prince of Hohenlohe-Langenburg and his wife Princess Alexandra of Saxe-Coburg and Gotha, on 5 February 1916 at Coburg. Friedrich and Marie Melita had four children.[citation needed]
When the Head of the House of Schleswig-Holstein-Sonderburg-Augustenburg, Albert, Duke of Schleswig-Holstein, died on 27 April 1931, Friedrich's father Friedrich Ferdinand became the Head of the House of Oldenburg and inherited the title of Duke of Schleswig-Holstein.[citation needed]
On 21 January 1934, Duke Friedrich Ferdinand died, and Friedrich became head of the House of Schleswig-Holstein-Sonderburg-Glücksburg.[citation needed]
Duke Friedrich died on 10 February 1965 in Coburg, Bavaria, West Germany.[citation needed]