Frederick Charles of Schleswig-Holstein-Sonderburg-Plön (August 4, 1706, Sønderborg – the night of October 18–19, 1761, Traventhal), 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 (or Holstein-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.