非弹性散射是指一种粒子动能不守恒的散射，出现在化学、核物理及粒子物理中，与其相对的是弹性散射，散射前后粒子动能守恒。

在非弹性散射中，部份粒子的能量增加或是减少了。非弹性散射以往会视为和动力学中非弹性碰撞有关，但二者的概念有很大的差异：非弹性碰撞是指碰撞前后的总动能不守恒。一般而言，由非弹性碰撞产生的散射会是非弹性散射，不过因为弹性碰撞会使二个粒子交换能量，由弹性碰撞产生的散射也可能是非弹性散射，例如康普顿散射。

若粒子能量的变化远小于粒子本身的能量，一般会称为准弹性散射。

非弹性散射常出现在电子和光子的交互作用中。当高能的光子碰撞到自由电子，因此转移能量，称为康普顿散射，若是一个具有相对论能量的电子碰撞到可见光或红外线的光子，电子会将能量转换给光子，称为逆康普顿散射。

In chemistry, nuclear physics, and particle physics, inelastic scattering is a fundamental scattering process in which the kinetic energy of an incident particle is not conserved (in contrast to elastic scattering). In an inelastic scattering process, some of the energy of the incident particle is lost or increased. Although the term is historically related to the concept of inelastic collision in dynamics, the two concepts are quite distinct; the latter refers to processes in which the total kinetic energy is not conserved. In general, scattering due to inelastic collisions will be inelastic, but, since elastic collisions often transfer kinetic energy between particles, scattering due to elastic collisions can also be inelastic, as in Compton scattering (see below).