The A4361 is blocked whilst emergency services attend a serious collision.
Wiltshire Air Ambulance landed in a field alongside the scene of the crash between Wroughton and Avebury at around 12.30pm.
Police have closed the main road between Broad Hinton and Winterbourne Bassett.
At least one person is believed to have sustained serious injuries. They have been taken to the Major Trauma Centre at Southmead Hospital in Bristol.
A spokesperson for Wiltshire Police said: “We are advising drivers to avoid travelling along the A4361 – the route has been closed in both directions from Avebury to Winterbourne Bassett following a serious road traffic collision.
“The closure will be in place for some hours and motorists are advised to seek alternative routes.
“We are advising that there is no access to Swindon via Avebury and that motorists should take the A346 instead.”
Bus company Stagecoach says their service 49 has been diverted around the scene due to the road closure.