A contactor is an electrically-controlled switch used for switching an electrical power circuit. They are typically controlled by a circuit which has a much lower power level than the switched circuit, such as a 24-volt coil controlling a 230-volt motor switch.

Contactors come in many forms with varying capacities and features. Unlike a circuit breaker, a contactor is not intended to interrupt a short circuit current. Contactors range from those having a breaking current of several amperes to thousands of amperes and 24 V DC to many kilovolts.