负阻特性也称为负微分电阻特性，是指一些电路或电子组件在某特定端口的电流增加时，电压反而减少的特性。一般的电阻在电流增加时，电压也会增加，负阻特性恰好与电阻的特性相反。电压随电流变化的情形可以用微分电阻（differential resistance）r表示：

没有一个单一的电子组件，可以在所有工作范围都呈现负阻特性，不过有些二极管（例如隧道二极管）在特定工作范围下会有负阻特性。 图一用共振隧道二极管说明其负阻特性。有些气体在放电时也会出现负阻特性。而一些硫族化物的玻璃、有机半导体及导电聚合物也有类似的负阻特性。负阻组件在电子学中可制作双稳态的切换电路及频率接近微波频率的震荡电路。

In electronics, negative resistance (NR) is a property of some electrical circuits and devices in which an increase in voltage across the device's terminals results in a decrease in electric current through it.

This is in contrast to an ordinary resistor in which an increase of applied voltage causes a proportional increase in current due to Ohm's law, resulting in a positive resistance. While a positive resistance consumes power from current passing through it, a negative resistance produces power. Under certain conditions it can increase the power of an electrical signal, amplifying it.