Mr Macron's party has filled the political space created by the disarray within the Socialists and the Republicans.
Disillusion towards old parties, a will to give Macron a stable majority, as well as a lack of interest due to a lacklustre campaign - just a month after a heated presidential election - could explain French voters' apathy.
Around half of REM's candidates are virtual unknowns drawn from diverse fields of academia, business or local activism. They started arriving Monday at the National Assembly to learn their way around before the first parliament session next week.
Les Republicains and its allies are on track to secure around 125 seats, well down on its 200 in the previous parliament but higher than earlier polls had suggested.
French authorities have slightly corrected the voting results Monday after final count showed a Socialist won by 54 votes over a conservative in the oversea region of Mayotte.
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. Its centrist ally, the Modem party, got 40 seats (6 percent).
"During their exchange, he conveyed France's full support to Mali's president during this ordeal", said Macron's office.
Female representation in the National Assembly has risen steadily, from 12.3 percent at the 2002 election to 38.6 percent this time.
Government spokesperson Christophe Castaner said the French disinterest "is as an additional responsibility and it will allow Emmanuel Macron, Edouard Philippe to never forget that deep down there is no victory tonight and the real victory will be in five years when things will really have changed".
But Jean-Luc Melenchon, the far-left candidate he defeated in May, said an all-powerful Mr Macron "is going to end up believing he walks on water". Ultimately, he will be judged on his results, and whether he can make a proper dent in France's unemployment rate of 10%.
Workers unions have already criticized the labor reform and the president's decision to skirt normal procedure to pass changes that would short-circuit extended debate and nix amendments.
LREM, which won an overwhelming majority in Sunday's ballot, had the highest proportion of women elected, at 47 percent. Some political analysts have called for the elections to be held on the same days as the presidential elections to prevent electoral "fatigue".
Confusion also played a role, according to Frederic Dabi, of the IFOP polling firm.
This victory for the LREM - a movement launched by Macron less than a year ago, and fielding a team of political novices - is being viewed as a slap for mainstream French parties.
The party will also be looking at whether it continues to follow a strategy of calling itself "neither Right nor Left" with both right-wing anti-immigration policies and left-wing protectionist policies.
- Champions Trophy final: India lose to Pakistan by 180 runs
- Australia Optimistic About Confederations Cup
- 'Alt-Right' Condemned By Southern Baptist Convention
- 'Sombre' Britain prepares for historic Brexit talks
- Macron wins majority to push through reforms
- 79 dead, missing in wake of London high-rise fire
- Thomas shoots 63, trails Harman by one at US Open
- Camille Cosby Criticizes Judge, District Attorney
- Vice President Mike Pence Retains Outside Counsel in Russia Investigation
- After intense final, Pak-India players enjoy spirit of cricket