近地天体 （near-Earth object, NEO）为太阳系内其轨道接近地球的天体。所有近地天体的轨道近日点都小于1.3天文单位，它们包括数以千计的近地小行星、接近的彗星、和大到在撞击到地球之前还在太空时就能够被监测的流星体。现在广泛认为过去的天体撞击，对于地球的地质史和生物史有着重大的影响。自1980年代以后，由于逐渐认知到近地小行星和彗星的潜在危机，对近地天体的兴趣已逐渐增在，减缓威胁也在积极研究中。

近地天体中有部分的小行星轨道的近日点在距离太阳0.98和1.3天文单位之间。当一颗这样的近地小行星（NEA）被检测到，就会提交给位于哈佛-史密松天体物理中心的小行星中心编目登录。一些近地小行星的轨道会和地球轨道交会，所以它们有和地球碰撞的潜在危险。美国、欧洲联盟、和其它国家目前共同努力建构太空警卫，持续的监视这些近地小行星。

A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By definition, all NEOs have a closest approach to the Sun (perihelion) of less than 1.3 astronomical unit (AU). They include more than fourteen thousand near-Earth asteroids (NEAs), more than one hundred near-Earth comets (NECs), and a number of solar-orbiting spacecraft and meteoroids, large enough to be tracked in space before striking the Earth. It is now widely accepted that collisions in the past have had a significant role in shaping the geological and biological history of the Earth. NEOs have become of increased interest since the 1980s because of increased awareness of the potential danger some of the asteroids or comets pose, and mitigations are being researched. In January 2016, NASA announced the Planetary Defense Coordination Office to track NEOs larger than 30 to 50 meters in diameter and coordinate an effective threat response and mitigation effort.