Crews from St Mary’s, Redbridge, Totton and Eastleigh fire stations attended the incident.
The 53-year-old woman was pronounced dead at the scene by
South Central Ambulance Service paramedics.
A man was also treated for smoke inhalation at the scene.
The fire in the three-storey building was extinguished using four sets of breathing apparatus, two hose reel jets, two main jets and ventilation fans.
Firefighters conducted community safety activities prior to the stop message at 04:33.
Hampshire Police and Fire Investigation Officers will attend the scene to ascertain the cause of the fire.
Smoke alarms provide valuable early warning of a fire. We ask that residents ensure they have working smoke alarms, test them regularly and prepare an escape plan, considering exit routes and the closing of fire doors.
If you suspect a fire don’t hesitate to call.