Stephane Pinta, a painting specialist with the Turquin gallery in Paris, said an auctioneer spotted the painting earlier this year while inspecting the woman’s house in Compiegne in northern France and suggested she bring it to experts for an evaluation.
The painting, titled Christ Mocked, measures about 10in by 8in (24cm by 20cm).
Art experts say it is probably part of a larger diptych that Cimabue painted in around 1280, of which two other panels are displayed at the Frick Collection in New York and the National Gallery in London.
The painting’s discovery has sent ripples of excitement throughout the art world, according to art experts.
The auction took place near Chantilly, north of Paris, and it was expected that a major art museum could purchase it for €4 million to €6m (£3.4 million to £5.1 million).
In the event, bidding went way over the estimate.
Dominique Le Coent of Acteon Auction House, who sold the work to an anonymous buyer near Chantilly, north of Paris, said the sale represented a "world record for a primitive, or a pre-1500 work".
"It's a painting that was unique, splendid and monumental. Cimabue was the father of the Renaissance. But this sale goes beyond all our dreams," Le Coent said.
Until recently, the work hung on a wall between the kitchen and the dining room in a house in Compiegne.
Its owner had considered it of little importance.
Specialists at the Turquin gallery initially examined the painting and concluded with “certitude” that it bore the hallmarks of Cimabue.