Steph Catley scored the only goal from the penalty spot for the Aussies.
The Republic of Ireland suffered a narrow 1-0 defeat to Australia in their first ever Women's World Cup game.
A 52nd minute penalty converted by Steph Catley was the difference between the two sides in Sydney after a foul by Marissa Sheva.
Ballinasloe's Heather Payne played the full 90 minutes for Vera Pauw's side.
Earlier, co-hosts New Zealand caused a huge upset in the tournament's opening game.
Hannah Wilkinson's goal gave the co-hosts a 1-0 victory over Norway in Auckland, their first-ever World Cup win in 16 attempts.
Our team 🇮🇪
— Ireland Football ⚽️🇮🇪 (@IrelandFootball) July 20, 2023
10' | Ireland have settled well in a fantastic atmosphere as the Fields of Athenry rings around the stadium for the first time {0-0}#COYGIG | #FIFAWWC pic.twitter.com/ltegHqWwCE
75,784 people filled Stadium Australia in Sydney, with thousands of them Irish fans.
The record is still held by a Barcelona/Wolfsburg match last year, when 91,648 people turned out.
A minute's silence was held ahead of both fixtures after a deadly shooting in Auckland.
Two people were killed close to the Norwegian team hotel.
Ireland's next game will be against reining Olympic champions Canada next Wednesday with a 1:00pm kick off Irish time.
Australia top Group B while group opponents Canada and Nigeria - meet in the morning.
Our Women's World Cup coverage is with thanks to The Bed Shed Kilbeggan, who offer an express delivery and assembly service right across the Midlands for the full range of over 40 beds and mattresses on offer in their showroom. . .find The Bed Shed on Facebook and Instagram for our latest offers.
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