The result, based on official figures and poll projections, fully redraws France’s political landscape, sidelining the Socialists and Republicans who have alternated in power for decades.
French President Emmanuel Macron’s parliamentary majority comes just weeks after his own presidential victory.
His La Republique en Marche party has won well over 300 seats in the 577-seat national assembly.
French Prime Minister Edouard Philippe addressed the country after the result.
“This Sunday, you have given a clear majority to the President of the Republic and to the Government. This majority will have a mission, to act for France. By their votes, the French people have, in their large majority, preferred hope over anger, optimism over pessimism, confidence over retreat.”
Many of the party’s new recruits are political unknowns, and Mr Philippe has attributed their election to a public appetite for new faces in parliament.
Polls project President Macron’s party and its Modem allies will win between 355 and 365 seats in the 577-seat lower house, fewer than previously forecast.
Macron wins massive majority in parliament
The conservative Republicans and their allies would form the largest opposition bloc, with 125 to 131 seats.
The Socialist Party, which has been in power for the past five years, and its partners would secure 41 to 49 seats, their lowest ever in the postwar Fifth Republic.
The interim president of the Republic on the Move party, Catherina Barbaroux, has hailed the election result as historic.
“For the first time in the Fifth Republic, there will be a profound renewal of the National Assembly. It will be more diverse, younger, strengthened with diverse professional, voluntary and political experience. But, above all, and let me be personally very delighted, it’s a historic moment for the representation of women in the National Assembly,” she said.
Mr Macron’s party has filled the political space created by the disarray within the Socialists and the Republicans.
Jean-Christophe Cambadelis, the leader of the French Socialist Party, has resigned after he was knocked out of the running for parliament in last week’s first round of voting.
He said the party will have to rebuild from the top down, suggesting what he terms “the left” needs to change radically if it still wants to be a strong force in French politics.
“Emmanuel Macron’s triumph is unquestionable. The left’s defeat is unavoidable. The rout of the Socialist Party is irrevocable. The right is facing real failure. And the populists from all sides are pushed to the margins,” he said.
Nationalist leader Marine Le Pen has won a seat in the National Assembly for the first time.
Her National Front party clinched at least eight seats in total, a result she has celebrated, but it may disappoint supporters, who were dreaming of her winning the presidency a month ago.
Ms Le Pen has cited record low levels of voter participation – less than half of the eligible voters – minimised the significance of Mr Macron’s victory.
“Abstention has today broken new records. The low turnout shows that mistrust towards politics has reached a peak. The election of Mr Macron to the presidency of the Republic seems to have sent the country into a state of indifference and weariness vis-a-vis the Republic, which is very worrying. Massive abstention considerably weakens the legitimacy of the new National Assembly.”
The scale of the victory gives the president a strong platform, though, for enacting campaign promises to revive France’s fortunes.
He has promised to clean up politics and relax regulations which, investors say, shackle the eurozone’s second-biggest economy.
But the abstention rate shows he must go carefully in a country with strong trade unions and a history of street protests that have forced past governments to dilute new legislation.