Douglas Buchanan, a spokesman for the D.C. Fire and Emergency Medical Services Department, said firefighters found the woman in her second-floor apartment. She was the lone occupant.
Fire officials said on Twitter that the woman died shortly after arriving at a hospital. She was later identified as Kim Simone Day, 57, of Southeast Washington.
Buchanan said the fire was quickly extinguished and investigators are working to determine a cause. No other injuries were reported.