威廉·勒尼德·马西（William Learned Marcy，1786年12月12日绍斯布里奇 - 1857年7月4日鲍尔斯顿斯帕），美国政治家，曾任纽约州州长、美国战争部长和美国国务卿。

William Learned Marcy (December 12, 1786 –July 4, 1857) was an American statesman, who served as U.S. Senator, Governor of New York, U.S. Secretary of War and U.S. Secretary of State. In the latter office (1853–1857) under President Franklin Pierce, he resolved a dispute about the status of U.S. immigrants abroad and negotiated the last major acquisition of land for the continental United States (Gadsden Purchase). He also directed U.S. diplomats to dress in the plain style of an ordinary American rather than the court-dress many had adopted from Europe.