Part of State Highway 1 north of Auckland is blocked following a fatal crash just north of the Puhoi turnoff.
Police said a motorcyclist had been killed in a head-on collision with a car.
Four people in the car received minor to moderate injuries.
Diversions are in place, but the road is expected to be closed for several hours.
Police said the diversions would significantly add to motorists' travelling times and are advising people to either delay their travel or avoid the area.
