The A342 at Lower Everleigh near Pewsey is closed after a collision involving two cars.
The incident occurred shortly before 3.30pm at the dip prior to the Indian restaurant in the 50mph zone. It involved a gold Ford Focus and a black Volkswagen Golf.
The passenger of the Ford Focus has suffered a serious head injury and the driver of the Golf, an elderly female, has minor injuries.
The air ambulance and police are still at the scene and the road between Upavon and the A338 is currently closed.