Firefighters managed to save the main stone structure of he medieval cathedral of Notre-Dame, including its two towers, but the spire and roof collapsed, the BBC reports.
The fire was declared under control almost nine hours after it started.
The cause is not yet clear but officials say it could be linked to extensive renovation works under way. No casualties were reported, a firefighter was seriously injured while tackling the blaze.
French President Emmanuel Macron has vowed to rebuild the 850-year-old Gothic building after a major fire partially destroyed the Paris landmark.
Visiting the site on Monday night, Mr Macron said the "worst had been avoided" with the preservation of the cathedral's main structure as he pledged to launch an international fundraising scheme for the reconstruction.
"We'll rebuild this cathedral all together and it's undoubtedly part of the French destiny and the project we'll have for the coming years," said Mr Macron.
"That's what the French expect [and] because it's what our history deserves," he added, calling it a "terrible tragedy".
Billionaire François-Henri Pinault, chairman and CEO of the Kering group that owns the Gucci and Yves Saint Laurent fashion brands, has already pledged €100m towards rebuilding Notre-Dame, AFP news agency reports.