Schack Carl, rigsgreve (von) Rantzau or Carl Schack Rantzau-Ascheberg (11 March 1717, Ascheberg estate, Holstein – 21 January 1789, Menerbes, France) was a Holstein-born Danish officer and statesman. He is notable for his friendship with Johann Friedrich Struensee and his role in the coup which led to Struensee's fall from power.