Lucy Page Mercer Rutherfurd (26 avril 1891-31 juillet 1948) était la secrétaire puis la maîtresse du président américain Franklin Delano Roosevelt.
Elle était aux côtés de Roosevelt le jour de son décès le 12 avril 1945. Elle était la femme de Winthrop Rutherfurd (1862–19 mars 1944).
Eleanor Roosevelt hired Lucy Mercer (1891-1948) as her social secretary in 1913, shortly after the Roosevelts moved to Washington when Franklin became Assistant Secretary of the Navy. In 1916, while Eleanor and the children were in Campobello, a romance blossomed between Franklin and Lucy. Eleanor discovered letters between the two in September 1918 as she unpacked Franklin’s bags following his inspection trip to Europe. The affair forever changed the nature of Franklin and Eleanor’s marriage.
Eleanor offered Franklin a divorce, but if they remained married, he was never to see Lucy again. Lucy became governess for the children of Winthrop Rutherford, a wealthy widower whom she married in 1920.
Franklin and Lucy maintained some limited contact by letter during the 1920s and 1930s, and following Winthrop Rutherford’s death in 1944, Franklin and Lucy began to see each other in person. Lucy was at Warm Springs on April 12, 1945 when FDR was stricken with the cerebral hemorrhage from which he died later that day. Although Eleanor felt betrayed when she learned of the visits, Lucy gave FDR friendship and companionship in his last months.