An Australian side missing injured superstar Sam Kerr made a winning start to their home Women's World Cup on Thursday with a nervy 1-0 victory over debutants Ireland in front of a pulsating 75,000-strong Sydney crowd.

Stand-in skipper Steph Catley calmly slotted home a penalty in the 52nd minute in the only goal of a full-blooded game that sprung to life in the second half.

It ensured three points in a tough Group B as the Matildas kick-started their mission to sweep past the quarter-finals for the first time.

But they had to do without Chelsea striker Kerr, their all-time leading goal-scorer who was ruled out before kick-off until at least their third game with a calf injury.

The setback means the skipper will also miss the clash against Nigeria in a week's time, with their medical team to make an assessment before their final group clash, against Olympic champions Canada.

Despite her absence, deafening cheers in a throbbing Stadium Australia greeted the players, with a record crowd of 75,784 for a women's game in Australia -- plenty of them Irish fans in full voice.

It surpassed the 50,629 who flocked to see the Matildas in a Melbourne friendly against France last week that the home side won 1-0.

That victory came on the back of recent wins over Spain and European champions England, with many seeing Australia as among the title favourites.

Manchester City's Mary Fowler, who scored the winner against France, started in place of Kerr with Arsenal's Catley assuming the captain's armband.

They had their first sniff of goal in the 16th minute after a cagey opening, but Clare Hunt couldn't control her header from Kyra Cooney-Cross's corner and the ball flew wide.

Ireland did well to blunt Australia's usual high-octane game, defending deep, as Kerr looked on nervously from the sidelines.

Hayley Raso had a decent opportunity, shaving the upright with a header, while Caitlin Foord's left-foot strike hit the side-netting.

Some clattering challenges were made by both sides and the yellow card finally came out for Ireland's Denise O'Sullivan, herself the casualty of a fierce tackle in an abandoned friendly against Colombia last week that saw her taken to hospital.

The breakthrough came seven minutes into the second half when Raso was bundled over in the box by Marissa Sheva.

With no Kerr, Catley stepped up to belt her spot-kick into the left-hand corner and send the crowd wild, with the relief palpable.

It sparked the game into life and Fowler almost made it 2-0 soon after, but her effort flew over the bar.

Ireland refused to go away and launched waves of attacks in a desperate push for the equaliser, but the home side threw players behind the ball and clung on to ensure an unconvincing victory.