The 62-year-old was found unconscious by firefighters inside the ground floor property in Wester Hailes Park, Edinburgh, at around 1.30pm yesterday.
He was taken to the city’s Royal Infirmary suffering from smoke inhalation but later died, police said.
The blaze was extinguished by two fire crews and officers are investigating the circumstances of the fire along with police. It is not thought to be suspicious.
A Scottish Fire and Rescue Service spokeswoman said: “We received a call to a fire in a ground floor flat in Wester Hailes Park in Edinburgh.
“We had crews from Sighthill and Tollcross immediately mobilised. On arrival they donned breathing apparatus and extinguished the fire using one line of hose.
“We had one male casualty discovered as crews searched the property. He had suffered from smoke inhalation and was unresponsive.
“Fire and ambulance personnel worked together on the casualty at the scene.He was subsequently transferred to the Royal Infirmary in a critical condition.
“Fire and police officers are now working to establish the cause of the fire. Adjoining flats were searched as a matter of course and fire safety advice given by Scottish Fire and Rescue Service personnel.”