The fire started around 8:30 a.m. at a home on Idora Avenue in the Forest Hill neighborhood.
It started in the back of the home and investigators say it appears to have been accidental.
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The woman was trapped on the second floor and had to be rescued. She died after being pulled from the home.
"Our thoughts and prayers are with the family and the community," SFFD said in a tweet.
The victim has not been identified.