大西洋主义（Atlanticism）是一个西欧和北美国家（特别是美国和加拿大），在政治、经济、军事防卫等议题上互相合作的哲学。其宗旨是维护相关国家的安全，及保卫「民主、个人自由与法治」的价值。 其名称是来自于将西欧与北美相隔开来的大西洋。与大西洋主义立场相对的是大陆主义。

北大西洋理事会（North Atlantic Council）是大西洋两岸最早提供讨论及决策的政府层级论坛。知名的大西洋主义者有前英国首相布莱尔、前英国首相布朗、兹比格涅夫·布热津斯基和哈维尔·索拉纳。北大西洋公约组织是个大西洋主义组织，而F-35闪电II攻击战斗机则是个大西洋主义计划。波兰和罗马尼亚等一些东欧的领导人曾公开表达强烈的大西洋主义观，但没有任河人是住在西欧（或北美）地区。

Atlanticism is a belief in the importance of cooperation between Europe and the United States and Canada regarding political, economic, and defense issues, with the purpose of maintaining the security and prosperity of the participating countries, and to protect the values that unite them. The term can be used in a more limited way to imply support for the North Atlantic military alliance, or in a more expansive way implying broader cooperation, deeply shared values, a sense of community, and some degree of integration between the two sides of the ocean. The term derives from the Atlantic Ocean that separates the two continents. In practice the philosophy of Atlanticism encourages active North American, particularly US, engagement in Europe and close cooperation between the two sides of the ocean. This manifested itself most strongly during the Second World War and in its aftermath through the establishment of various euro-Atlantic institutions, most importantly NATO and the Marshall Plan.