In Paris, Gregoire - a 48-year-old former deputy of outgoing Socialist Mayor Anne Hidalgo - beat right-wing ex-minister Rachida Dati, 60.
Former justice and culture minister Dati, a protegee of now-convicted ex-President Nicolas Sarkozy, had hoped to seize Paris for the right and become its second female mayor in a row.
“Paris has decided to stay true to its history,” Gregoire told a cheering crowd.
In Marseille, the leftist incumbent, Benoit Payan, was comfortably re-elected, beating far-right candidate Franck Allisio, according to projections from several pollsters.
‘Reasons to hope’
In the northern port city of Le Havre, declared presidential candidate Edouard Philippe was re-elected, provisional results showed.
Philippe, a centrist former Prime Minister, is seen as one of the strongest opponents to the RN’s potential presidential pick - whether three-time presidential candidate Marine Le Pen, 57, or her 30-year-old lieutenant Jordan Bardella.
“There are reasons to hope,” he told his supporters.
“We, the people of Le Havre, say this to the French today: yes, there are reasons to hope in our creative and ambitious youth, capable of imagining and building a new world that is more respectful of human beings than our own, more mindful of our planet and our future,” he said.
Le Pen’s far-right party had been hoping for wins in southern urban hubs today, but early projections largely quashed those ambitions.
A right-wing candidate beat the RN in the naval port city of Toulon, while a far-right candidate lost to a Communist in Nimes, a city of 150,000, pollsters suggested.
The far-right party saw its candidate re-elected a week ago in the southern city of Perpignan of 120,000 inhabitants - the largest in France to be run by the far-right party so far.
Overall turnout was 57% - the country’s lowest in local polls bar the Covid pandemic-affected last edition in 2020.
-Agence France-Presse