Cristiano Ronaldo was sent off for an elbow as Portugal blew another chance to qualify for the 2026 World Cup after losing 2-0 to Ireland on Thursday.

Troy Parrott struck twice in the first half to keep Ireland's hopes of reaching next summer's tournament alive with a famous victory against Ronaldo and his teammates in a Group F qualifier.

With Portugal chasing a way back into the game, their frustrated captain Ronaldo was dismissed for elbowing Dara O'Shea in the back.

Portugal still lead the group on 10 points, two ahead of Hungary and three in front of Ireland, with one match remaining on Sunday.

The team that finishes top reaches the World Cup automatically, while second-place teams reach the play-offs.

"This is probably the best night I have had in my entire life, I have no words to describe it," AZ Alkmaar striker Parrott said. "I am overwhelmed. I don't know what words to use, but I am over the moon."

Portugal spurned one chance to qualify in October when they drew with Hungary, and another went begging at the Aviva Stadium as Ireland recorded an unforgettable triumph.

Heimir Hallgrimsson's side knew they had to avoid defeat to still have a chance of qualification after Hungary, second, beat Armenia 1-0 earlier on in Group F. Ireland last reached the World Cup in 2002.

Portugal controlled the ball in the opening stages as Ireland sat back, content to keep the visitors at bay and cause trouble on the counter.

Parrott headed Ireland into a surprise lead after 17 minutes from close range, when Liam Scales nodded the ball back across the face of goal from a corner.

Joao Neves fired narrowly wide and Joao Felix headed over as Portugal looked for an equaliser and turned up the pressure.

Chiedozie Ogbene came close at the other end as he got in behind and flashed a shot against the post in front of a fired-up home crowd.

Parrott doubled Ireland's lead on the stroke of half-time, cutting in from the left and driving past goalkeeper Diogo Costa low at his near post. (AFP)