A plug valve is a rotary valve with a closing part or plunger shape, which is opened or closed by rotating 90 degrees so that the passageway on the plug is connected with or separated from the passageway on the valve body.

The shape of the valve plug can be cylindrical or conical. In the cylindrical valve plug, the channel is generally rectangular; In a tapered valve plug, the channel is trapezoid. These shapes make the construction of the plug valve lightweight. It is most suitable as a cutting and switching medium and a shunt application, but depending on the nature of the application and the erosion resistance of the sealing surface, it can sometimes be used for throttling.