Son of August III of Poland and Maria Josepha of Poland.
In 1758 he was elected to succeed the former Duke of Courland, Ernst Johann von Biron, who had been unseated for his extravagant and autocratic habits. However, in 1763 he was himself dethroned and replaced by Biron, by the influence of Empress Katharina of Russia. In Boswell's words "Prince Charles of Saxony, Duke of Courland, of which last dignity the Russian tyrant has deprived him."1
Boswell was introduced to the Prince on September 29, at an entertainment at the Palace of the Late Prince Maurice of Anhalt-Dessau (d. 1760), and he described him as "a charming prince, perfectly gay and affable". The palace had succeeded to Princess Wilhelmine, "who gave there this day a splendid entertainment" in honour of Carl Christian. At the ball that same evening, "The Duke of Courland danced the best of any man I ever saw."