粒子加速器（英语：particle accelerator）是利用电场来推动带电粒子使之获得高能量。日常生活中常见的粒子加速器有用于电视的阴极射线管及X光管等设施。被加速的粒子置于抽真空的管中，才不会被空气中的分子所撞击而溃散。在高能加速器里的粒子使用四极磁铁（quadrupole magnet）聚焦成束，粒子才不会因为彼此间产生的排斥力而散开。

粒子加速器有两种基本型式，环形加速器和直线加速器。

A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to nearly light speed and to contain them in well-defined beams. Large accelerators are best known for their use in particle physics as colliders (e.g. the LHC at CERN, RHIC at Brookhaven National Laboratory, and Tevatron at Fermilab). Other kinds of particle accelerators are used in a large variety of applications, including particle therapy for oncological purposes, and as synchrotron light sources for the study of condensed matter physics. There are currently more than 30,000 accelerators in operation around the world.