Alexander Charles, Duke of Anhalt-Bernburg (2 March 1805 – 19 August 1863) was a German prince of the House of Ascania.

Alexander Charles was born at Ballenstedt on 2 March 1805 as the second (but eldest and only surviving) son of Alexius Frederick Christian, Duke of Anhalt-Bernburg, by his first wife Maria Fredericka, daughter of William I, Elector of Hesse.

In Gottorp on 30 October 1834 Alexander Karl married Princess Friederike of Schleswig-Holstein-Sonderburg-Glücksburg, daughter of Frederick William, Duke of Schleswig-Holstein-Sonderburg-Glücksburg and his wife Princess Louise Caroline of Hesse-Kassel; she was also a sister of the later King Christian IX of Denmark.

By November 1855 the Duke was confined to Schloss Hoym due to a progressive mental illness (some sources state that he had schizophrenia).

There, Alexander Karl spend the rest of his life under medical care in the company of his chamberlain, the painter Wilhelm von Kügelgen.