The richest man in Europe is one of several billionaires who have pledged to donate millions to help restore devastated Notre Dame Cathedral.
Huge parts of the 850-year-old building in Paris have been destroyed in the blaze, including the iconic spire and roof.
But president Emmanuel Macron said: "I am solemnly telling you tonight: this cathedral will be rebuilt by all of us together" as he described Notre Dame as "our history".
And now Bernard Arnault's family and his LVMH luxury goods group have said he will donate 200 million Euros (£170 million) to restore the iconic cathedral.
He said in a statement: "The Arnault family and the LVMH group would like to show their solidarity at this time of national tragedy, and are joining up to help rebuild this extraordinary cathedral, which is a symbol of France, of its heritage and of French unity."
Mr Arnault, who Forbes says is the richest person in Europe, is CEO of LVMH, whose subsidiaries include Dior, Marc Jacobs, Bulgari, Givenchy Parfums, Moët & Chandon and Mercier.
The 70-year-old instantly became the biggest benefactor of an appeal launched by Macron.
But he's not the only millionaire who has offered to help with big financial pledges.
And François-Henri Pinault, chairman and CEO of international luxury group Kering, which includes Gucci and Saint Laurent, he and his family will donate 100 million Euros (£86 million) to help repair the historic landmark.
"My father [François Pinault] and I have decided to release as of now from the funds of Artemis a sum of 100 million euros to participate in the effort that will be necessary for the complete reconstruction of Notre Dame," the businessman wrote in a statement within hours of the blaze.
Dad-to-five Mr Arnault, born in Roubaix, about 140 miles northwest of Paris, is said to be worth some £68 billion. It makes him the fourth richest person in the world, Forbes says.
In April last year, he became the richest person in fashion.
His LVMH was created in 1987 under the merger of Louis Vuitton with Moët Hennessy.
France’s Heritage Foundation has launched a "national collection" on its website.
And Valerie Pecresse, president of the Ile-de-France region, has unveiled a budget of 10 million euros of "emergency aid to help the archdiocese to start the work."
Ms Pecresse added: "This reconstruction, which will obviously be very expensive, will mobilise a whole country."
Anne Hidalgo, the Mayor of Paris, said she wanted to organise an "an international conference of donors" to welcome "experts who are able to raise funds."
The investigation into the fire, meanwhile, continues.
Detectives today began interviewing specialist restorers directly linked to the fire.