Fire crews were called to Eggborough, to the south of North Yorkshire, at about 5.30pm on Monday after reports of smoke coming from a house.
North Yorkshire Police have confirmed that officers found the body of a woman in her 80s inside the house.
A spokesperson said: "Police were called by North Yorkshire Fire and Rescue Service to a property in Eggborough at 5.37pm on December 30 after they attended a report of smoke coming from a property.
"On arrival officers found a woman in her 80s inside the property who was sadly pronounced dead by the ambulance service.
"Enquiries are currently ongoing to determine the cause of her death and the circumstances that led to it."
York station manager Bob Hoskins said that fire investigation officers are looking into the cause of the fire.