战略防卫计划(Strategic Defense Initiative (SDI))，亦称星战（Star Wars）。
美国提议的防止核袭击的战略防御系统。由雷根总统在1983年提出，为的是截取飞行中的洲际弹道飞弹以防止羽翼丰满的苏联的袭击。这一阻击包括了当时还未能完全发展起来的太空基地和地球基地的雷射作战站等技术。战略防卫计画的空中计画部分使之沿用流行电影「星球大战」的名字而被戏称为「星战」。虽然国会在1980年代批准了首批资金，但该计画激起了激烈的争论，并遭到广泛批评，被认为是不可行的。该计画还因可能加速武器备战和破坏武器控制条约而被谴责。该计画早期的发展很成功，并在苏联解体後被用於防范敌对国家的小规模突袭或单个偶尔发送的导弹。1999年美国宣布将实施一个新的战略防卫计画。亦请参阅antiballistic missile。
English version：
Strategic Defense Initiative (SDI)
Proposed U.S. strategic defense system against nuclear attacks. Announced by Pres. Ronald Reagan in 1983, SDI was intended to defend the U.S. from a full-fledged Soviet attack by intercepting ICBMs in flight. The interception was to be effected by technology then not yet developed, including space- and earth-based laser stations and air- and ground-based missiles. The space component of SDI led to its being derisively dubbed “Star Wars” after the popular film. Though Congress granted initial funding in the mid-1980s, the program aroused heated debate; widely criticized as unworkable, it was also decried for accelerating the arms race and undermining arms-control agreements. Early development efforts were largely unsuccessful, and after the fall of the Soviet Union the project was scaled back to focus on protecting the U.S. from a small attack by a rogue nation or a single accidentally launched missile. In 1999 the U.S. again announced its intent to implement a new antimissile defense program. See also antiballistic missile.