Officers were called to a two-vehicle collision in Countess Road at around 11.30pm last night.
The collision involved a black Audi and a black BMW and the driver of the Audi, a man in his 20s, suffered suspected serious pelvic injuries and was taken to hospital.
The driver of the BMW, a 35-year-old man, was arrested on suspicion of drink driving and is currently in custody at Melksham Police Station.
A spokesman for Dorset & Wiltshire Fire and Rescue Service said: “At 23:40 fire control received a call from Wiltshire Police requesting our attendance at the scene of a road traffic collision involving two cars.
“Crews from Salisbury, Andover and Ludgershall attended and used hydraulic cutting equipment to release one male casualty from one of the vehicles.
“Both vehicles involved were isolated and made safe and the casualty was conveyed to hospital by road ambulance.”
The road was closed to allow collision investigation enquiries to be carried out and was reopened at around 8am this morning.
An investigation is now ongoing and police would urge anyone with information, including anyone who might have dash cam footage which could assist their enquiries, to call 101, quoting reference 54210096027.