The lively West Ham forward smashed the ball into the top left cornerfrom 20 metres to spare Les Bleus blushes in the Stade de Francepacked with 75,115 fans.
Olivier Giroud had headed France ahead in the 57th off Payet’s cornerkick, but Bogdan Stancu converted a penalty seven minutes later frothe stubborn Romanians.
Antoine Griezmann was earlier denied by the post for the French butStancu had also blown a major chance at the start of each half on theother end.
France are bidding to win a third straight big home event after Euro1984 and the 1998 World Cup, and got an early lead in Group A aheadof their other games against Albania and Switzerland.
Didier Deschamps’ team dominated but the defence looked shaky attimes and the high-class attack didn’t make more out of the chancesthey got - almost all set up by Payet - against a Romanian defencewhich had let in just two goals in their 10 qualifiers.
"The result matters most. Not everything was perfect, far from it.But the victory is positive and its very important to begin with avictory," Deschamps said.
"In had no doubts over Dimitiri Payet that he can make thedifference," he added. "It was a wonderful goal."
Payet said: "There was a lot of stress and pressue. If someone wouldhave told me I wouldn’t have believed it. It all come out with thegoal."
The opening game was preceded by a short and vibrant opening ceremonyfor the 24-team tournament until July 10, featuring cancan dancersand DJ David Guetta.
Security was tight at the vast arena which had been one of thetargets during the terror attacks in Paris on November 13, 2015.
The predominantly French crowd appeared to chant their anthem withsome extra defiance before kick-off but then quickly held its breathas the high pressing Romanians almost spoilt the party.
Stancu’s point-blank range effort at the far right post was somehowkept out by Hugo Lloris, and second later Florin Andone’s headersailed just over the bar.
Arsenal’s Giroud had a first chance before Atletico Madrid’sGriezmann, under pressure from Napoli defender and Romania captainVlad Chiriches, was denied by the right post in the 14th.
Griezmann’s shot off Payet’s low cross was slightly deflected to flyinches right, and Giroud then headed high in stoppage time.
Like in the first half, the French were almost caught out cold byStancu early in the second. Steaua’s Nicolae Stanciu found thecompletely unmarked Genclerberiligi forward in the area but hevolleyed wide after trying to control the ball with his chest.
That woke up Les Bleus again, and goalkeeper Ciprian Tatarusanu madea fantastic save with his feet to thwart Paul Pogba’s low drive.
But the Fiorentina keeper didn’t look good on the ensuing cornerwhich Payet whipped to the far left post where Giroud beat Tatarusanuwith a header for an overall deserved French 1-0 lead in the 57th.
The joy however lasted a mere seven minutes. Patrice Evra slightlytripped Staciu and Stancu finally found the net on his third bigchance, calmly slotting the penalty into the bottom right corner for1-1 as Lloris went the other way.
Deschamps brought on youngsters Kingsley Coman and Anthony Martialfor Griezmann and Pogba but the game seemed heading towards a drawbefore Payet came to the rescue to crown his own performance and giveFrance the perfect start they wanted.
"It hurts to lose in the 89th minute - but it was a fabulous strikefrom a wonderful player," Romania coach Anghel Iordanescu said.