Cristiano Ronaldo's Portugal battled back to beat the Czech Republic 2-1 thanks to substitute Francisco Conceicao's late winner in their opening Group F game on Tuesday.
Roberto Martinez's side went a goal down against the run of play after a brilliant strike just after the hour by Czech Republic's Lukas Provod.
Portugal had dominated possession but couldn't find the goal their superiority deserved, with their record scorer Ronaldo going close on several occasions.
The Al Nassr man, who was top scorer in last season's Saudi Pro League, was denied twice in the first half by saves from Czech keeper Jindrich Stanek and the 2016 European champions were caught by a sucker punch when Provod scored with a sweet strike from outside the box on 62 minutes.
Stanek then handed the Portuguese a lifeline when he parried a Nuno Mendes header against defender Robin Hranac and the ball bounced into the back of the net.
Portugal substitute Diogo Jota thought he had grabbed the winner when he pounced to nod home after a powerful Ronaldo header had struck the post but a VAR check ruled that Ronaldo had been offside in the build-up.
It was left to another substitute, Conceicao, to make sure that Ronaldo got his record sixth European Championship campaign off to a winning start as he scored from close range in stoppage time.
Portugal's Spanish coach Martinez said the 21-year-old Porto winger deserved his moment of glory.
"Francisco is the ultimate example of earning it. He deserves to be here and showed he is ready to help the group," Martinez told reporters.
"Francisco is doing what he's been doing for the past four months in his club team. This is not easy. He showed character and showed his worth because he was allowed to be here.
"Francisco is a very mature player. He plays very direct. He's got a nose for danger in the box.
"For a national team coach and having a player that showed what he showed, it's very important."
The former Belgium coach praised his players' attitude in fighting back against a tough Czech team.
"We conceded – a goal down – and managed to win the game," he said. "We lost against Slovenia after conceding the first goal, Croatia the same thing happened [both in friendlies]. Today we conceded and won.
"We all want to grow together during this tournament, we played the perfect 90 minutes to be able to grow – next we face off against Turkey."
Portugal meet Turkey on Saturday, while the Czech Republic face Georgia, who lost 3-1 to the Turks in Tuesday's earlier kick off.
