墨西哥战争(Mexican War)，亦称美墨战争（Mexican-American War）。
美国和墨西哥在1846～1848年间发生的战争。起因於1845年美国并吞德克萨斯後所发生的一场边界纠纷。墨西哥声称德克萨斯的南部边界是努埃塞斯河，而美国则坚持是格兰德河。当墨西哥拒绝斯利德尔秘密协商纠纷和用3,000万美金购买新墨西哥和加利福尼亚的要求後，总统波克派遣泰勒将军率领部队进占两河之间有争议的地区。1846年4月墨西哥军队越过格兰德河袭击泰勒的军队，美国国会在5月通过了宣战的决议。泰勒接获进攻墨西哥的命令後，在1847年2月的布埃纳维斯塔战役夺占了蒙特雷并击溃圣安纳所带领的大批墨西哥人军队。波克後来命令司各脱将军从海路绕到韦拉克鲁斯，占领该市，并进军内陆逼近墨西哥城。司各脱照原定计画前进，在塞罗戈多和孔特雷拉斯遭遇墨西哥的反抗军队，於同年9月攻陷墨西哥城。墨西哥於是签署了「瓜达卢佩伊达尔戈和约」，割让的土地范围包括现今新墨西哥、犹他、内华达、亚利桑那、加利福尼亚、德克萨斯和科罗拉多等州几乎全部的土地。在这场战争中，约有13,000名美国士兵伤亡，其中1,700人是因疾病身亡。这场战争将泰勒将军造就为国家英雄，并重新开启「密苏里妥协案」中已获解决的扩张奴隶制议题。
English version：
Mexican War
War between the U.S. and Mexico, 1846-48. It grew from a border dispute after the U.S. annexed Texas in 1845; Mexico claimed the southern border of Texas was the Nueces River, while the U.S. claimed it was the Rio Grande River. A secret mission by John Slidell to negotiate the dispute and purchase New Mexico and California for up to $30 million was aborted when Mexico refused to receive him. In response to the snub, Pres. James Polk sent troops under Zachary Taylor to occupy the disputed land between the two rivers. In April 1846 Mexican troops crossed the Rio Grande and attacked Taylor's troops; Congress approved a declaration of war in May. Ordered to invade Mexico, Taylor captured Monterrey and defeated a large Mexican force under Antonio Santa Anna at the Battle of Buena Vista in February 1847. Polk then ordered Gen. Winfield Scott to move his army by sea to Veracruz, capture the city, and march inland to Mexico City. Scott followed the plan, meeting resistance at Cerro Gordo and Contreras, and entered Mexico City in September. Under the Treaty of Guadalupe Hidalgo, Mexico ceded nearly all of present New Mexico, Utah, Nevada, Arizona, California, Texas, and Colorado. Casualties included about 13,000 American deaths, all but 1,700 of which were caused by disease. The war, which made a national hero of Taylor, reopened the slavery-extension issue supposedly settled by the Missouri Compromise.