在物理学中，准粒子或称集体激发是一种发生在微观复杂系统的突现现象。例如固态系统中会好像存在着另一种虚拟的粒子。 以电子在半导体中的运动为例，电子在运动过程中受到来自原子核以及其它电子的作用，然而其行为可以视作带有不同质量的自由电子。 这个带有不同质量的「电子」称为「准电子」（electron quasiparticle）。 另外一个实例是在半导体的价带集体行进的电子，其行为可以视作半导体中存在着带正电的电洞往反方向运行。 其它的准粒子包括声子（来自固态系统中原子的振动）、电浆子（来自电浆的振荡）等许多种类。

In physics, quasiparticles and collective excitations (which are closely related) are emergent phenomena that occur when a microscopically complicated system such as a solid behaves as if it contained different weakly interacting particles in free space. For example, as an electron travels through a semiconductor, its motion is disturbed in a complex way by its interactions with all of the other electrons and nuclei; however it approximately behaves like an electron with a different mass traveling unperturbed through free space. This "electron" with a different mass is called an "electron quasiparticle". In another example, the aggregate motion of electrons in the valence band of a semiconductor is the same as if the semiconductor contained instead positively charged quasiparticles called holes. Other quasiparticles or collective excitations include phonons (particles derived from the vibrations of atoms in a solid), plasmons (particles derived from plasma oscillations), and many others.