The spire of the cathedral in the northern French city of Rouen caught fire on Thursday.
Rouen Mayor Nicolas Mayer-Rossignol posted an image of smoke rising from the cathedral on X, formerly Twitter, adding that the cause of the blaze was "unknown at this stage."
The cathedral was painted several times by French impressionist Claude Monet in the late 19th century.
BFM television channel showed a dark plume of smoke rising from the spire. A local official said the building had been evacuated and emergency services were on the scene.
