Former Pescara and Sampdoria man Birkir Bjarnason's equaliser gave Iceland an unlikely point against Portugal.
Iceland went into the match knowing a victory would see them become the smallest nation ever to win a European Championship match, the previous record having been set by Wales on Saturday.
Portugal’s talisman Cristiano Ronaldo was making his 127th appearance, equalling Luis Figo’s record.
It was almost a dream start for the debutants, as Gylfi Sigurdsson cut inside Danilo, but Rui Patricio beat away his near post effort and the Swansea City man couldn’t convert the rebound.
Portugal had a number of corners, but Hannes Þór Halldórsson’s first task was to beat away a left-footed strike from Vieirinha.
With 20 minutes played, Ronaldo swung in a glorious cross for Nani, but Halldórsson somehow managed to get a foot to the header to keep the score at 0-0. Ronaldo himself headed over three minutes later.
The Real Madrid man should have opened the scoring, but he could only come up with a fresh air shot after running onto a long ball from Pepe.
Portugal were ramping up the pressure, and Nani opened the scoring with a low finish after being picked out by André Gomes.
Shortly after the break, Birkir Bjarnason wrote himself into Icelandic footballing history by scoring their first ever goal at a major tournament.
Vieirinha got caught under the ball, leaving Basel midfielder free at the back post, and he made no mistake, side-footing home on the volley to send the Icelandic fans into raptures.
Portugal were dominating possession, but Aron Gunnarson’s long throws were creating danger whenever Iceland managed to break forward.
Ronaldo almost got a late winner, but he was uncharacteristically poor with his header, and Halldórsson managed to save.
Substitute Alfreð Finnbogason could have made things even better for his side, but his shot was straight at Patricio.
In added time in added time, Ronaldo made Iceland sweat with two free-kicks, but both struck the wall and the debutants held on for a memorable point.
Portugal 1-1 Iceland
Nani 31 (P) Bjarnason 50 (I)
Portugal: Rui Patricio; Vieirinha, Carvalho, Pepe, Guerreiro; João Mário (Quaresma, 76), Danilo, André Gomes (Eder, 84); João Moutinho (Sanches, 70); C. Ronaldo, Nani
Iceland: Halldórsson; Saevarsson, Sigurdsson, Gudmundsson (E. Bjarnason, 90), Bjarnason; Sigthorsson (Finnbogason, 81), Sigurdsson, Arnason; Gunnarsson, Skulason
Referee: Çakir [TUR]