The euro was last 1.2 percent higher against the dollar at $1.0855, not far from the 5-1/2-month high of $1.0935 it reached after the initial indications from the Sunday vote gave victory to Macron, as predicted by weeks of polling.
The same polls showed Macron defeating Le Pen by as much as 30 percentage points in two weeks' time, suggesting players can buy back into the currency. The euro's session high briefly put the currency up about 2 percent against the greenback.
Sunday's outcome reduced the prospect of an anti-establishment shock on the scale of Britain's vote last June to quit the European Union and the election of Donald Trump as US president.
The euro's dip from its session high likely indicated profit-taking rather than doubts about a Macron victory over Le Pen in the second round, said Richard Franulovich, senior currency strategist at Westpac Banking Corp in New York.
"The news of Macron winning is now priced in," he said. "The risks of a disintegration of the euro have been removed."
Strategists at French bank Credit Agricole said their positioning measures showed the euro had been bought for most of the last week, suggesting that many players had already closed previous short bets against the currency.
As markets globally were comforted by the results of the French vote, investors abandoned the perceived security of the yen. The euro was last up 2.1 percent against the Japanese currency at 110.41 yen and the dollar was up 0.8 percent against the yen at 109.92 yen after touching a nearly two-week high of 110.62.
The results of the vote were soothing in part because fears of a potential Le Pen runoff with far-left candidate Jean-Luc Melenchon, both of whom distrust the European Union, did not play out.
"That 'nightmare' scenario of Le Pen versus Melenchon is off the table," said Chris Konstantinos, director of international portfolio management at RiverFront Investment Group in Richmond, Virginia.
The dollar index, which measures the greenback against a basket of six major rivals, was last down 0.9 percent at 99.115 after touching a roughly 5-1/2-month low of 98.908.