Mathilde de Morny (26 May 1863 – 29 June 1944) was a French aristocrat and artist. She was also known by the nickname "Missy" or by the artistic pseudonym "Yssim" (an anagram of Missy), or as "Max", "Uncle Max" (French: Oncle Max), or "Monsieur le Marquis". Active as a sculptor and painter, Morny studied under Comte Saint-Cène and the sculptor Édouard-Gustave-Louis Millet de Marcilly.