A one-piece headlight adapter, and a two-piece headlight adapter system, is used to connect the existing vehicle headlight controls and power supply with a snowplow wiring harness. An adapter only connects the controls and power supply for one headlight to the wiring harness. Two adapters, one for each headlight, create an adapter system. The adapter system allows the vehicle operator to control the snowplow headlights from the inside of the vehicle. One version of an adapter is a three-component adapter that includes one connection to the vehicle headlight, one connection to the headlight controls, and one connection to the wiring harness. Another version of the adapter is a five-component adapter that includes high and low beam connections to the vehicle headlight, high and low beam connections to the headlight controls, and one connection to the wiring harness. In each version, the connections of the adapter include a connection to the common ground which ensures a fixed potential on which the snowplow headlights operate.