The winning margin is lower than some expected, with turnout down from 2012. The party was formed just over a year ago, and half of its candidates have little or no political experience.
The result has swept aside all of the mainstream parties and gives the 39-year-old president a strong mandate in parliament to pursue his pro-EU, business-friendly reform plans.
The comfortable majority of La République en Marche (Republic on the Move or LREM) and MoDem – surpassing the 289-seat threshold required to control the National Assembly – will be a big blow to traditional parties on both the left and right.
The conservative Republicans and their allies could form a large opposition block, with 125-131 seats. But this figure is down from 200 seats in the last parliament.
The Socialists, who were in power for the past five years, alongside their partners, looked set to get only 41-49 seats – their lowest tally ever.
Socialist leader Jean-Claude Cambadélis announced his retirement from post, and urged the left “to change everything, its form and its substance, its ideas and its organisation”.
The far-right National Front (FN) party won eight seats, but it had set its sights on 15.
FN leader Marine Le Pen, 48, has won a seat in parliament for the first time, representing Henin-Beaumont, a depressed former mining town in the north. But two of her top aides, including her deputy leader, were eliminated.
Ms Le Pen said President Macron may have got a large parliamentary majority, but “he must know that his ideas are not of the majority in the country and that the French will not support a project that weakens our nation”.
What are President Macron’s reforms?
The new French president needed a majority to push through the changes that he promised in his campaign, which include:
Budget savings of €60bn (£51bn; $65bn) in the next five years
Cutting the number of public servants by 120,000
Reforming the labour market and generous state pension schemes, bringing them into line with private schemes
The interim LREM leader, Catherine Barbaroux, said the party could now start work towards changing France:
“Far from postures, our members of parliament, through their multiple experiences, will vote for laws to unlock our economy, free up our energies, create new solidarities and protect the French,” she said.
The LREM win is big enough to give the new president a good chance of weathering the inexperience and diversity of his new political army, and to push forward with bold and controversial labour reforms, says the BBC’s Lucy Williamson in Paris.