Thousands of police surrounded the Stade de France ahead of the gala opener amid widespread security fears, with the month-long football fiesta kicking off in style in Paris despite terror concerns and widespread strikes.
Payet crossed for Olivier Giroud to head France into a 57th-minute lead at the national stadium, but Bogdan Stancu equalised from the penalty spot after a clumsy foul from Patrice Evra on Nicolae Stanciu.
However, West Ham playmaker Payet conjured up a long-range wonder strike a minute from time to ensure France -- one of the favourites for the title along with Germany and Spain -- made a triumphant start.
WATCH: France 2-1 Romania: Euro 2016 - Full Highlights
French manager Didier Deschamps, who is bidding to repeat France's triumphs at Euro '84 and the 1998 World Cup on home soil, admitted he was a relived man after Payet's heroics.
"It's good to get the win," Deschamps told TF1. "This Romania team isn't easy to play, we knew that, even if we were able to score the opening goal.
"We struggled to get out the blocks but the reward was at the end. It's a very good thing to have won the first match, to start us off in the competition."
More trouble in Marseille
Some 90,000 police and security guards are protecting the 10 stadiums and surrounding fan zones.
But violence erupted in Marseille where England fans were involved in a second day of fighting, while a hint of scandal tainted the tournament when Spain goalkeeper David De Gea strongly denied links to a sex scandal.
The first big test of the security dragnet came as England fans and Russian supporters squared off in Marseille, where their countries play on Saturday.
Riot police had to separate English and Russian supporters, police prefect Laurent Nunez told AFP, adding that seven arrests had been made.
Meanwhile, Manchester United goalkeeper De Gea appeared at a Spain press conference to dismiss reports that he had organised a party where women were allegedly forced to have sex against their will.
"I am the first one to be surprised by this report. I deny it, it is false and nothing more, it is a lie and false," De Gea said at Spain's team base.
Eldiario.es news website said the name of De Gea and Athletic Bilbao's Iker Muniain appeared in the testimony of a "protected witness" as part of an investigation into Ignacio Allende, a Spanish porn producer who was detained in April for alleged sexual abuse of minors and spreading child pornography.
The witness reportedly said she and another woman were forced to participate in a party in 2012 organised by De Gea, in which they both had sex with footballers.
After France and Romania opened proceedings, the newly expanded 24-team tournament kicks into gear with six more games on a star-studded weekend.
England's prolific new strike partnership of Premier League top-scorer Harry Kane and Leicester City title-winning hero Jamie Vardy will hope to outgun Russia on Saturday.
Also in England's group, Real Madrid's Gareth Bale will headline Wales' opener in their first appearance in a major championship since the 1958 World Cup.
The Welsh play Slovakia, also making their first appearance at the finals.
On Sunday, world champions Germany open their campaign against Ukraine, and Bayern Munich's Polish striker Robert Lewandowski will aim to spoil Northern Ireland's first ever appearance in the Euros finals.
