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.
Prince Friedrich was born on 23 August 1891 at in Schleswig-Holstein, Kingdom of Prussia. He was the fifth child and only son of Frederick Ferdinand, Duke of Schleswig-Holstein-Sonderbug-Glücksburg and Princess Karoline Mathilde of Schleswig-Holstein-Sonderburg-Augustenburg.
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.
Friedrich married his second cousin, Princess Marie Melita of Hohenlohe-Langenburg, daughter of Ernst II, Prince of Hohenlohe-Langenburg and Princess Alexandra of Saxe-Coburg and Gotha, on 5 February 1916 at Coburg. Friedrich and Marie Melita had four children.
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.
On 21 January 1934, Duke Friedrich Ferdinand died, and Friedrich became head of the House of Schleswig-Holstein-Sonderburg-Glücksburg.
Duke Friedrich died on 10 February 1965 in Coburg, Bavaria, West Germany.