With tears in his eyes, Macron said that "the worst has been avoided" thanks to the work of firefighters who battled for hours to save the Gothic cathedral's two towers and facade.
He vowed to draw on "the best talent" to rebuild what had been destroyed.
"What happened tonight in Paris and at Notre-Dame Cathedral is a terrible tragedy," Macron said.
"The worst was avoided even if the battle has not been completely won yet and the next few hours will be difficult."
The 41-year-old president described the 850-year-old monument at the heart of Paris as "the epicentre of our life" and the cathedral of "all the French", whether religious or not.
He said that "starting tomorrow" he would launch an international appeal for the restoration of the beloved church.
"And we will rebuild Notre-Dame because it is what the French expect," he said, flanked by Paris Mayor Anne Hidalgo and Paris Archbishop Michel Aupetit.