阵亡将士纪念日（英语：Memorial Day，是美国联邦法定节日，原名纪念日，或悼念日，又译国殇纪念日）是美国的一个纪念日，每年5月的最后一个星期一（2015年是5月25日）悼念在各战争中阵亡的美军官兵。全国悼念时间于美东时间下午3时开始。

阵亡将士纪念日不单是对美国人展现爱国情操的一个重要节日，在民间更是代表夏季正式开始。不少海滩、游乐场、小岛的夏日渡轮等等，都会由该星期的周末开始营运。而且由于连续有3日假期，令不少美国民众到郊外烧烤野餐、到海边玩乐或者参观博物馆等等，导致交通挤塞颇严重。

Memorial Day is a federal holiday in the United States for remembering the people who died while serving in the country's armed forces. The holiday, which is observed every year on the last Monday of May, originated as Decoration Day after the American Civil War in 1868, when the Grand Army of the Republic, an organization of Union veterans founded in Decatur, Illinois, established it as a time for the nation to decorate the graves of the war dead with flowers. By the 20th century, competing Union and Confederate holiday traditions, celebrated on different days, had merged, and Memorial Day eventually extended to honor all Americans who died while in the military service. It typically marks the start of the summer vacation season, while Labor Day marks its end.