Fredericka of Saxe-Gotha-Altenburg (17 July 1715 – 2 May 1775), was a German noblewoman member of the House of Wettin and by marriage Duchess of Saxe-Weissenfels.
Born in Gotha, she was the fifteenth of nineteen children born from the marriage of Frederick II, Duke of Saxe-Gotha-Altenburg and Magdalena Augusta of Anhalt-Zerbst.
From her eighteen older and younger siblings, only eight survived to adulthood: Frederick III, Duke of Saxe-Gotha-Altenburg, William, John August, Christian William, Louis Ernest, Maurice, Augusta (by marriage Princess of Wales), and John Adolph.