The Duchess of Saxe-Altenburg refers to a title held by the female members of the House of Saxe-Altenburg, a German noble family. This duchy was part of the larger region of Thuringia and existed from the early 19th century until the end of the German monarchies after World War I. The title was often associated with various marriages and alliances within European royalty. The most notable Duchess of Saxe-Altenburg was Maria Theresa, who became the duchess through her marriage to Joseph, Duke of Saxe-Altenburg. The duchy was known for its cultural contributions and played a role in the political landscape of Germany during its existence.