Macron handily defeated far-right National Front leader Marine Le Pen in Sunday's presidential runoff, and now must pull together a majority of lawmakers for his year-old political movement to run in the mid-June legislative election.
Valls, a center-leaning politician in favor of relaxing labor protections, had already thrown his support behind Macron before the presidential election after losing to Benoit Hamon in the Socialist primary.
Valls told RTL radio on Tuesday that Macron's victory over far-right leader Marine Le Pen in the presidential runoff on Sunday was a blow to populism in Europe, and gave a "terrific" image of France overseas.
Indeed, there is some scepticism about Macron's ability to win a majority with candidates from his centrist En Marche movement alone, meaning he might have to form a coalition.
Le Pen, leader of far-right party the National Front, had accused Macron of being "weak" on Islamist terrorism shortly after she scooped 21.4 per cent of the popular vote in the first round of voting, on April 23. His rivals now will be motivated to keep Macron from making further gains during the two-round parliamentary election. The euro too is expected to gain ahead as Macron is a follower of the European Union unlike Le Pen who is in favor of "Frexit".
After the first round of the French election, sources on and close to the ECB Governing Council told Reuters many rate-setters saw scope for sending a small signal in June towards reducing monetary stimulus.
Mr Farron said: "I would like to congratulate Emmanuel Macron on his election as France's new president". 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.
While his supporters were jumping for joy at the Louvre and commentators all over the world were hailing Emmanuel Macron's victory as a triumph for liberal and centrist values, a majority of French people won't have seen it as a cause for celebration.
Emmanuel Macron gave a rather solemn victory speech on Sunday night and there are several reasons why he was right to rein in his celebrations.
Foreign policy chief Federica Mogherini took up the refrain "Vive la France, Vive l'Europe" with a picture of her beaming side by side with Macron at the World Economic Forum.
Something essential about Ms Le Pen, and the National Front, had been revealed to France. On the one hand, voters in big cities came out strongly in favour of Macron's pro-European vision, while on the other hand Marine Le Pen's anti-immigration and pro-nationalist agenda appealed to many in rural as well as in the poorer and industrial north-east. France's CAC 40 index, which last week touched the highest level since early 2008, slipped 0.8 percent to 5,391 on Monday.