Frederick Charles, Duke of Schleswig-Holstein-Sonderburg-Plön

Frederick Charles of Schleswig-Holstein-Sonderburg-Plön, known as Friedrich Karl or Friedrik Carl of Holstein-Plön, was a member of a cadet branch of the Danish royal family and the last duke of the Duchy of Schleswig-Holstein-Sonderburg-Plön, a Danish royal prince, and a knight of the Order of the Elephant. When he died without a male heir born of his marriage to Countess Christine Armgard von Reventlow, rule of the Duchy of Holstein-Plön returned to the Danish crown.