近藤效应（Kondo effect）是指在高电导无磁金属母体中磁性杂质原子对传导电子散射几率的增大。

在某一特征温度TK(所谓近藤温度)以下，稀磁合金的剩余电阻率随温度的降低而反常增大。1964年，近藤淳从理论上阐明了该效应的形成机制：由于孤立磁性原子与传导电子之间存在RKKY相互作用，围绕磁性原子的传导电子的自旋将反平行极化，从而屏蔽磁性原子的磁矩，并形成一个多体单态。其他传导电子与这个多体单态之间不再有“自旋相同，空间回避”的限制，结果，磁性杂质对传导电子的散射变得更为有效，电阻率增大。

In physics, the Kondo effect describes the scattering of conduction electrons in a metal due to magnetic impurities, resulting in a characteristic change in electrical resistivity with temperature.

The effect was first described by Jun Kondo, who applied third-order perturbation theory to the problem, which predicted that the scattering rate of conduction electrons of the magnetic impurity should diverge as the temperature approaches 0 K. The temperature dependence of the resistivity including the Kondo effect is written as: