The woman, believed to have been in her sixties, died at the scene of the blaze in Kirkcaldy, Fife.
An investigation is now under way to establish the cause of the fire.
The Scottish Fire and Rescue Service (SFRS) said it was called to the flat in Kinninmonth Street at about 1.50am.
Two crews from Kirkcaldy and another from Burntisland attended.
Four firefighters using breathing equipment entered the “heavily smoke-logged” property to conduct a search-and-rescue operation. Crews extinguished the flames using two hose reel jets.
Firefighters rescued the woman from the property and, along with paramedics, gave her emergency first aid. Despite their efforts, she died at the scene.
Fire investigation officers have launched a probe into the incident. They are said to be working closely with Police Scotland.
SFRS group manager Alex Smart said: “The loss of life through fire in the home is utterly devastating and the thoughts of everyone are with those involved in this tragedy.
“This tragic loss of life must always bring home the importance of working together to prevent fires and raise awareness of how to be safer from the risk of fire in the home.
“SFRS crews routinely conduct free home fire safety visits to help householders identify risks and take the simple steps needed to reduce the chance of fires.”
Free home safety fire visits can be arranged by calling 0800 0731 999, texting FIRE to 80800 or visiting www.firescotland.gov.uk
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