11 fire appliances have been called to a major fire in a thatched cottage in Rushall, near Pewsey.
Fire crews were alerted at 2pm, and are still working at the scene now.
No one is believed to be inside the detatched property, and no rescue has been attempted.
Wayne Jones, of Wiltshire Fire and Rescue Service said: "There are 75 personel dealing with the incident at a thatched property measuring 25m by 15m.
"The fire is in the roof area of the property, and we are currently attempting to create creat breaks in the thatch to remove any additional fuel to the fire, to protect it from spreading further.
"At this stage we can't say how long it could go on for."
The fire was reported by a passing motorist.