The staggering sum has been raised less than 24 hours after fire ravaged France's world famous medieval cathedral.
Apple, L'Oreal and the oil company Total are among the household names which have declared they will give tens of millions of euros each.
France and Europe's richest man Bernard Arnault - reported to be worth £69bn - has pledged €200m (£173m), while François-Henri Pinault, the billionaire fashion boss of Hollywood star Salma Hayek, is to write a check for €100m (£86m)
Tim Cook, Apple CEO, said: "We are heartbroken for the French people and those around the world for whom Notre Dame is a symbol of hope.
"Relieved that everyone is safe. Apple will be donating to the rebuilding efforts to help restore Notre Dame’s precious heritage for future generations."
Mr Pinault, 56, was one of the first to come forward following what newspapers in France are calling a “national tragedy”.
The chairman and chief executive of the Kering group, which owns brands such as Gucci and Yves Saint Laurent, is worth an estimated £19bn.
In a statement announcing his financial pledge, he said: "This tragedy strikes all the French and beyond all those who are attached to spiritual values. Faced with such a tragedy, everyone wants to revive this jewel of our heritage as quickly as possible.
"My father and I have decided to release… €100m to participate in the effort that will be necessary for the complete reconstruction of Notre Dame."
The donation was quickly followed by Mr Arnault.
The 70-year-old head of the LVMH luxury goods group 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."
Meanwhile, smaller donations are expected to flood in as part of a national subscription scheme launched by president Emmanuel Macron on Tuesday.
Elsewhere, the country’s Fondation du Patrimoine, a private organisation which works to protect French heritage, said it would be starting an international appeal; while the website Dartagnans, which is dedicated to preserving France's cultural heritage, has announced it has already received around £24,500 in donations.
But even more may well be needed. Early estimates suggest rebuilding of the cathedral will cost seal billion pounds and take more than 20 years.
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