The A43 between the BP Garage in Brackley and the B4525 near Syresham is expected to remain closed both ways for a couple of hours following an incident this morning.
Two vehicles were involved in a serious collision at 8.30am and one of the drivers has been airlifted to hospital.
The road was closed to allow the air ambulance to land.
Officers from Northants Police are at the scene.
Northants Police are recommending motorists avoid the area.