场效应管（英语：field-effect transistor，缩写：FET）是一种通过电场效应控制电流的电子组件。

它依靠电场去控制导电沟道形状，因此能控制半导体材料中某种类型载流子的沟道的导电性。场效应晶体管有时被称为「单极性晶体管」，以它的单载流子型作用对比双极性晶体管。由于半导体材料的限制，以及曾经双极性晶体管比场效应晶体管容易制造，场效应晶体管比双极性晶体管要晚造出，但场效应晶体管的概念却比双极性晶体管早。

The field-effect transistor (FET) is a transistor that uses an electric field to control the shape and hence the electrical conductivity of a channel of one type of charge carrier in a semiconductor material. FETs are also known as unipolar transistors as they involve single-carrier-type operation. The FET has several forms, but all have high input impedance. While the conductivity of a non-FET transistor is regulated by the input current (the emitter to base current) and so has a low input impedance, a FET's conductivity is regulated by a voltage applied to a terminal (the gate) which is insulated from the device. The applied gate voltage imposes an electric field into the device, which in turn attracts or repels charge carriers to or from the region between a source terminal and a drain terminal. The density of charge carriers in turn influences the conductivity between the source and drain.