The result - as of midnight Sunday, Paris - based on official figures and pollster projections, redraws France's political landscape, humiliating the Socialist and conservative parties that alternated in power for decades until Macron's election in May.
Three pollsters projected that Macron's Republic on the Move (LREM) and its Modem allies would win 355 to 365 seats in the 577-seat lower house, fewer than previously forecast.
They predicted the conservative Republicans and their allies would form the largest opposition bloc with 125 to 131 seats, while the Socialist Party, 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 result, if confirmed, would give 39-year-old Macron one of France's biggest post-war majorities, strengthening his hand in implementing his programme of business-friendly reforms.
The assembly is set to be transformed with a new generation of lawmakers -- younger, more ethnically diverse and with far more women than the outgoing parliament.
But Macron's success was tempered by record low turnout of around 44 percent, leading opposition leaders to claim he had no groundswell of support.
The winning score was lower than forecast during the past week when some estimates suggested REM and its allies could secure as many as 470 seats.
"A clear majority has voted for us," REM spokesman Benjamin Griveaux told TF1, adding: "It will be a majority with an opposition and that's good news."
Desire for change
Just months ago, Macron was given little chance of becoming president, never mind controlling parliament, but he and the movement he founded 16 months ago have tapped into a widespread desire in France for wholesale change.
Prime Minister Edouard Philippe, the rightwinger chosen by Macron to lead the cabinet, said voters had chosen "hope over misery".
REM swept aside the rightwing Republicans and Socialists, but also the far-right National Front (FN) of Marine Le Pen -- whom he defeated in the presidential run-off -- which fell far short of its target.
Le Pen, who entered parliament for the first time in her career, told supporters her FN had won at least six seats -- but the party was certain to fall short of its target of 15 seats.
"We are the only force of resistance to the watering down of France, of its social model and its identity," she said defiantly.
Le Pen's victory in the northern former coalmining town of Henin-Beaumont was a rare bright spot for her nationalist and anti-EU party that was once hoping to emerge as the principal opposition to Macron.
The Socialists were the biggest losers of the night, punished by association with years of high unemployment, social unrest and lost national confidence.
The party shed around 200 seats after five years in power under former president Francois Hollande, leaving them with only around 45-50 seats.
"The rout of the Socialist Party is undeniable," said PS leader Jean-Christophe Cambadelis, who humiliatingly lost his seat in the first round and resigned his position on Sunday night.
Former Socialist prime minister Manuel Valls narrowly retained his seat in the Paris suburbs, but former education minister Najat Vallaud-Belkacem -- a one-time Socialist star -- was beaten by an REM candidate in the central city of Lyon.
The Republicans hung on to between 97 and 130 seats, down from over 200 in the last parliament, and remain the main opposition party.
The party had enough seats to "defend its convictions", said the party's leader for the elections, Francois Baroin, calling on Macron to heed the record-low turnout, which he said sent "a message".
"The task he faces is immense," he added.
Around half of REM's candidates are virtual unknowns drawn from diverse fields of academia, business or local activism.
They include celebrity mathematician Cedric Villani and female bullfighter Marie Sara, who failed in her attempt to beat senior FN figure Gilbert Collard by barely 100 votes in southern France.
The other half are a mix of centrists and moderate left- and right-wing politicians drawn from established parties including ally MoDem.
The hard-left France Unbowed also struggled to maintain the momentum it had during the presidential election. It was forecast to win only between 10 and 30 seats.
Jean-Luc Melenchon, the firebrand leader of the movement, won a seat from the southern city of Marseille on a promise to lead resistance to Macron's radical labour market reforms.
Melenchon highlighted the record low turnout, saying: "The French people is now engaged in a sort of civic general strike."
Apart from loosening labour laws to try to boost employment, Macron also plans measures to deepen European integration and an overhaul of the social security system.
His confident start at home, where he has concentrated on trying to restore the lost prestige of the president, and his bold action on the international stage has led to a host of positive headlines.
He won instant plaudits from France's closest ally Germany, with Chancellor Angela Merkel's spokesman hailing his "clear parliamentary majority."