Steph Catley ensured co-hosts Australia opened their World Cup campaign with a 1-0 victory over the Republic of Ireland — despite the absence of star striker and captain Sam Kerr.

Catley’s second-half penalty was enough to clinch three points for the Matildas in front of a record crowd of 75,784 at Stadium Australia in Sydney.

But they had to do it the hard way after their record goalscorer Kerr was ruled out of the first two Group B games with a calf injury suffered in training.

Stand-in skipper Catley, 29, said: "It's hard to put into words. It's been such a big build up for us. 

"We've had a lot of adrenaline and excitement coming into the game. We had some moments where we had to work through that.

"Obviously we didn't have Sammy [to take the penalty]. I felt confident to do it. 

"I've been practising a lot recently and was happy to take it. For it to be my first World Cup goal was really special."

Boss Tony Gustavsson added: "Tournament football is always about finding a way to win.

"There's been a lot challenges thrown at this team over the last 24 hours. An opening game at a home World Cup and then you add Sam's injury to that. 

"They stuck together and played as a team and that mental toughness I am proud of.

"It is devastating [for Sam] but the way she spoke to the team today says a lot about her as a person and as a captain for this team."

Vera Pauw’s side, making their debut at a major tournament, made life difficult throughout for a side ranked 10th by FIFA, 12 places above Ireland.

But despite a late flurry, they were unable to get themselves back on level terms and will now turn their attention to Wednesday's clash with Canada in Perth.

For Australia, there was relief after three hard-earned points were banked to match the feat of co-hosts New Zealand, who had earlier stunned Group A rivals Norway with a 1-0 victory in Auckland.