Margaret "Gretl" Stonborough-Wittgenstein (19 September 1882 – 27 September 1958) was a sister of the philosopher Ludwig Wittgenstein and the pianist Paul Wittgenstein and a member of the wealthy Viennese Wittgenstein family. She was the subject of a famous 1905 portrait painted for her wedding by the artist Gustav Klimt (Stonborough-Wittgenstein and other members of the Wittgenstein family were among Klimt's most important patrons), which was sold in 1960 by her son Thomas and may now be seen in the Alte Pinakothek gallery in Munich.