Princess Marie Radziwill (Marie Dorothée Élisabeth; née Castellane; 19 February 1840, château de Rochecotte – 10 July 1915) was a French noblewoman, a member of the house of Castellane. The famous dandy Boni de Castellane was her nephew.
The daughter of Henri de Castellane and Pauline de Talleyrand-Périgord, Marie de Castellane married prince Antoine Radziwill (1833–1904), a member of the House of Lords of Prussia and general à la suite of William I, German Emperor, at Sagan on 3 October 1857. They had four children: Jerzy (George) (1860–1914), Élisabeth (1861–1950), Helena (1874–1958) and Stanislas (1880–1920).
She spent a large part of her life in Berlin, where (according to Abel Hermant) she was "the Apis bull in person and the queen of Berlin".
From 1881 to 1886, she took on the restoration of the Radziwill castle at Nieswiez (Nesvizh, Belarus), allowing her to save its archives and library, add a terrace flanked by Neo Gothic tourelles and redesign the park in the English style (1878–1911).
In 1906 she published the Souvenirs of her grandmother, the duchesse de Dino and, in 1909, a Chronique de 1831 à 1862, also based on the duchess's papers. Her own memoirs were published in 1931 as Souvenirs de la princesse Radziwill (née Castellane) 1840–1873. Une française à la cour de prusse ("Memoirs of Princess Radziwill, née Castellane, 1840–1873: A Frenchwoman at the Court of Prussia").
- Günter Erbe: Das vornehme Berlin. Fürstin Marie Radziwill und die großen Damen der Gesellschaft 1871–1918. Köln u.a.: Böhlau, 2015.