在量子力学里，量子穿隧效应为一种量子特性，是如电子等微观粒子能够穿过它们本来无法通过的“墙壁”的现象。这是因为根据量子力学，微观粒子具有波的性质，而有不为零的机率穿过位势障壁。

量子穿隧效应（Quantum tunnelling effect），是一种衰减波耦合效应，其量子行为遵守薛丁格波动方程序。假若条件恰当，任何波动方程序都会显示出衰减波耦合效应。数学地等价于量子穿隧效应的波耦合效应也会发生于其它状况。例如，遵守马克士威方程组的光波或微波；遵守常见的非色散波动方程序的绳波或声波。

若要使穿隧效应发生，必须有一个2型介质的薄区域，像三明治一般，夹在两个1型介质的区域。2型介质的波动方程序必须容许实值指数函数解（上升指数函数或下降指数函数），而1型介质的波动方程序则必须容许行进波解。在量子力学里，从粒子运动这方面来说，1型介质区域是粒子总能量大于位能的区域，而2型介质是粒子总能量小于位能的区域（称为位势垒）。

Quantum tunnelling or tunneling (see spelling differences) refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. This plays an essential role in several physical phenomena, such as the nuclear fusion that occurs in main sequence stars like the Sun. It has important applications to modern devices such as the tunnel diode, quantum computing, and the scanning tunnelling microscope. The effect was predicted in the early 20th century and its acceptance as a general physical phenomenon came mid-century.