Emmanuel Macron won 66.1 percent of the vote against 33.9 percent for far-right leader Marine Le Pen in France's presidential election, final results from the interior ministry showed on Monday.
Macron's camp has said the names of Macron's 577 candidates for the legislative elections will be announced on Thursday.
Although every recent French presidential election has been followed by the winner's party going on to take control of parliament, the outcome this time around has been made murky by Macron's lack of an established base.
Outgoing Socialist President Francois Hollande is due to formally hand over power to Macron on Sunday. Le Pen came already burdened with a bulging portfolio of past racist comments that gave her an uphill struggle from the beginning, making it that much harder for her to cast herself as an unsullied champion of the disaffected voter.
The opponents of Macron likely to follow the policies of Donald Trump like Le Pen would like to take France out of worldwide institutions, including both the European Union and North Atlantic Treaty Organisation; block borders; curtail trade; and impose quasi-Marxist state-dominated economics.
Sylvie Goulard, a French deputy to the European Parliament, said Macron would make Berlin his first official visit, with perhaps a stop to see French troops stationed overseas as well. In fact, her party, the National Front - while undergoing what she calls "soul searching" and maybe even a name change - could well gain seats in the legislature in June.
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The Socialist Party, whose own candidate for president finished a distant fifth in the first round, is holding a meeting today of all its parliamentary candidates.
Trying to bring more people into her party will be key, and Le Pen is looking for "those who choose France, defend its independence, its freedom, its prosperity, its security, its identity, and its social model", she said Sunday. Speaking at a campaign event in Harrow, northwest London, the prime minister suggested that Mr Macron's landslide defeat of Marine Le Pen would strengthen France's hand in negotiations over Brexit.
"It mustn't become normal that right-wing extremists and populists achieve such strong results", Roth said.
German Chancellor Angela Merkel welcomed his win, but appeared cautious about proposals to support his economic plans either by relaxing European spending rules or with a dedicated stimulus fund.
Donald Tusk, EU Council president, also offered his congratulations, saying the French had chosen "liberty, equality and fraternity" and "said no to the tyranny of fake news".
On the financial front, European stock markets edged down in early trading as investors had been widely expecting Macron's victory.
One proponent of euro bonds told Reuters on Monday that Macron's clear win in Sunday's election could mark a step toward creation of such instruments.
Germany's DAX was down 0.3 percent at 12,683 and Britain's FTSE 100 was up 0.1 percent at 7,301.