大型电子正子对撞机（Large Electron-Positron Collider，简称：LEP）是欧洲核子研究组织（CERN）的粒子加速器之一，****年开始营运，位在瑞士和法国的边界附近，大型电子正子对撞机的周长长达27公里，专门加速电子和正子，是目前已建成的最高能量的轻子加速器，且迄今为止还保留着粒子加速器的速度纪录。在2000年末的时候，LEP被关停并拆解，以给在建的新的大型强子对撞机腾出轨道空间。

The Large Electron–Positron Collider (LEP) was one of the largest particle accelerators ever constructed.

It was built at CERN, a multi-national centre for research in nuclear and particle physics near Geneva, Switzerland. LEP collided electrons with positrons at energies that reached 209 GeV. It was a circular collider with a circumference of 27 kilometres built in a tunnel roughly 100 m (300 ft) underground and passing through Switzerland and France. LEP was used from **** until 2000. Around 2001 it was dismantled to make way for the LHC, which re-used the LEP tunnel. To date, LEP is the most powerful accelerator of leptons ever built.