未来某年的7月2日,美国各地的监视站发现一艘直径达数百英里的巨大飞船接近了地球。飞船发出的无线电信号干扰了地球的通信卫星信号,并放出了多艘直径达15英里的子飞船飞抵地球上各大城市的上空。外星飞船敌友未明,人们陷入了恐慌和迷惑。 电脑工程师戴维(杰夫•戈德布拉姆 饰)破译出外星人发出的无线电信号,其实是攻击的倒计时信号,他设法通知了前妻,总统的助理康妮,但是为时已晚,7月3日,外星人的飞船开始攻击地球,人类文明瞬间遭到巨大的打击和灾难。总统(比尔•普尔曼 饰)等人撤离到军事基地,指挥空军反击,却犹如以卵击石,毫无作用,军事基地也被摧毁,唯有飞行员史蒂文(威尔•史密斯 饰)设法诱使一架外星人战斗飞艇坠毁。 幸存者们逃到了秘密军事基地,在那里,科学家们一直在研究一艘50多年前坠毁的外星飞艇,致力于找出对付外星人的办法,那里也是人类最后的希望……On July 2nd, communications systems worldwide are sent into chaos by a strange atmospheric interference. It is soon learned by the military that a number of enormous objects are on a collision course with Earth. At first thought to be meteors, they are later revealed to be gigantic spacecraft, piloted by a mysterious alien species. After attempts to communicate with the aliens go nowhere, David Levinson, an ex-scientist turned cable technician, discovers that the aliens are going to attack major points around the globe in less than a day. On July 3rd, the aliens all but obliterate New York, Los Angeles and Washington, as well as Paris, London, Houston and Moscow. The survivors set out in convoys towards Area 51, a strange government testing ground where it is rumored the military has a captured alien spacecraft of their own. The survivors devise a plan to fight back against the enslaving aliens, and July 4th becomes the day humanity will fight for its freedom. July 4th is their Independence Day...