Adam Szalai and Zoltan Stieber scored second-half goals as Hungary stunned highly-fancied Austria 2-0 in their Group F opener in Bordeaux on Tuesday.
Austria, tipped as tournament dark horses, dominated the opening period but Szalai fired Hungary ahead on 62 minutes with Stieber wrapping up a shock victory over their old rivals late on in the 138th meeting between the sides.
Aleksandar Dragovic was sent off for Austria shortly after Szalai ended an 18-month goal drought as Hungary made a triumphant return to a major tournament having last featured at the 1986 World Cup.
Hungary goalkeeper Gabor Kiraly kept a clean sheet as he became the first 40-year-old to feature at the European Championship, surpassing Germany's Lothar Matthaus as the oldest player in tournament history.
Austria captain Christian Fuchs and winger Martin Harnik were the only two survivors from the country's debut campaign eight years ago named in Marcel Koller's starting line-up.
However, they were inches away from the perfect start when Bayern Munich star David Alaba went agonisingly close to justifying his billing as one of the potential stars of the tournament when his dipping left-footed strike from outside the area crashed against the post.
The versatile Alaba, operating in his customary central midfield with Austria, soon fired another warning to Hungary with a first-time strike at Kiraly after a threaded pass through from Marko Arnautovic.
Szalai miscued a header from a Balazs Dzsudzsak free-kick in a rare opening for Hungary, while Kiraly showed his reflexes remain sharp despite his advancing years to claw behind a low strike from Zlatko Junuzovic.
Arnautovic then slid a dangerous low ball across the face of goal as Austria continued to threaten, but Harnik lost his footing as he tried to slide home at the far post.
Hungary captain Dzsudzsak wasted arguably the best chance of the opening 45 minutes, though, as he screwed his shot wide of goal after he was picked out by Laszlo Kleinheisler on the right-hand side of the penalty area.
Dzsudzsak again took aim 10 minutes into the second period, his stinging 30-yard shot forcing Austria keeper Robert Almer to fist the punch behind for a corner.
And Hungary grabbed a surprise lead just beyond the hour when Kleinheisler slipped in Szalai, who was played onside by Fuchs, with the powerful striker poking the ball underneath Almer for his first goal at any level since December 2014.
Austria appeared to have levelled when Martin Hinteregger rifled in from the edge of the area, but referee Clement Turpin disallowed the goal for a foul on Tamas Kadar with Dragovic dismissed for a second booking.
And Stieber triggered delirious celebrations when he raced from just inside the Austria half to beat Almer three minutes from time with a sublime chip as Hungary completed a stunning upset for their first European Championship win since 1964.