More than 70 firefighters were called to a thatched roof blaze on North Lane in Clanfield in the early hours.
The roof of the detached property was well alight when the first firefighters arrived on the scene shortly before 1am.
Chalton Lane is closed in both directions between South Lane/East Meon Road and Sunderton Lane due to a building fire.
Fortunately, there are no reports of any injuries but nearby residents are asked to keep windows and doors closed because of the smoke, and to avoid the area due to a large number of emergency vehicles in attendance.
More than 12 fire engines were called to the scene, coming from Horndean, Havant, Waterlooville, Cosham, Fareham, Hayling Island, Wickham, Southsea and Droxford fire stations.

Specialist resources from Eastleigh, Portchester and Alton were also required, as well as an aerial ladder.
Crews have been tackling the fire using hose reels and jets, allowing firefighters wearing breathing apparatus sets to conduct a salvage operation within the two-storey property on North Lane.
Both the roof and first floor have been destroyed in the fire with the ground-floor suffering smoke and water damage.
Crews from Hamble, Hightown and Bishop’s Waltham have been alerted to take over from those firefighters who were first on the scene and have been working for a number of hours.