Wiltshire Police were alerted by firefighters at 1.40am today to a fire at Thorley Court in Abbey Meads, Swindon.
A 32-year-old woman was brought out of the flat by the fire service and treated by
paramedics at the scene.
Sadly, she was pronounced dead at 2.12 am. Her next of kin have been informed but we await formal identification.
A 25-year-old man from the same flat was taken by helicopter to hospital in Bristol suffering from burns and the effects of smoke inhalation. He remains in a critical condition.
Officers forced their way into four flats to check that no one was trapped inside the building.
Crime scene investigators are attending and the building has been cordoned off.
It is too early at this stage in the investigation to confirm the cause of the fire but Wiltshire Police are working with Wiltshire Fire & Rescue Service to establish the circumstances.
"We would like to appeal to anyone who may have information, or who was in the area of Thorley Court between the hours of 2230 on Sunday 18 November and 0230 on Monday 19 November, to contact Wiltshire Police via 101 or call Crimestoppers on 0800 555 111.