French President Emmanuel Macron's party is on track for a parliamentary majority, exit polls suggest, weeks after his presidential victory.
Polls have his La République en Marche, alongside its MoDem allies, winning at least 355 seats in the 577-seat National Assembly.
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, if confirmed, sweeps all of the mainstream parties aside, and gives the 39-year-old president a strong mandate in parliament to pursue his pro-EU, business-friendly reform plans.
The second round of the parliamentary election was marked by low voter turnout, with an estimated record low of about 42%, down sharply on five years ago.
Correspondents say opponents of Mr Macron may simply have not bothered to turn out for the vote.
Prime Minister Edouard Philippe acknowledged the low turnout, promising his party would act for France as a whole.
Two polls projected La République en Marche (Republic on the Move or LREM) and MoDem combined winning 355-365 seats, which is more than the 289 seat threshold required to control the National Assembly.
It will be seen as 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, were predicted 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 looks set to get at least six seats, although it was aiming for 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".
People are looking at their new leader, and many more than voted for him are honestly impressed by his calibre. But many are also wondering: where do we go from here?
There is an unknown aspect to the coming mandate that sets it apart from all that went before.
President Macron's party didn't exist until he dreamed it up, and half of the new parliamentarians will need lessons (literally) in how to do their jobs.
And never before - at least not since Charles de Gaulle in 1958 - has a head of state had such a powerful majority, made up of men and women who depend on him so personally for their new careers.
"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.
At least half of LREM candidates are unknown, drawn from a range of backgrounds. They include a retired bullfighter, a Rwandan refugee and a mathematician.
Mr Macron sought gender equality in candidate selection, which resulted in a 50:50 male to female ratio.
Also read: The tricky issue of delimitation