电子（英语：electron）是一种带有负电的亚原子粒子，通常标记为。电子属于轻子类，以重力、电磁力和弱核力与其它粒子相互作用。轻子是构成物质的基本粒子之一，即其无法被分解为更小的粒子。电子带有1/2自旋，是一种费米子。因此，根据泡利不兼容原理，任何两个电子都不能处于同样的状态。电子的反粒子是正子，其质量、自旋、带电量大小都与电子相同，但是电量正负性与电子相反。电子与正子会因碰撞而互相湮灭，在这过程中，创生一对以上的光子。

由电子与中子、质子所组成的原子，是物质的基本单位。相对于中子和质子所组成的原子核，电子的质量显得极小。质子的质量大约是电子质量的1836倍。当原子的电子数与质子数不等时，原子会带电；称该带电原子为离子。当原子得到额外的电子时，它带有负电，叫阴离子，失去电子时，它带有正电，叫阳离子。若物体带有的电子多于或少于原子核的电量，导致正负电量不平衡时，称该物体带静电。当正负电量平衡时，称物体的电性为电中性。静电在日常生活中有很多用途，例如，静电油漆系统能够将瓷漆或聚氨酯漆，均匀地喷洒于物品表面。

The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value in units of ħ, which means that it is a fermion. Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all matter, electrons have properties of both particles and waves, and so can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a higher De Broglie wavelength for typical energies.