Having lost Karim Benzema, Paul Pogba and others to injury during a chaotic build-up to the tournament, France suffered another blow when Craig Goodwin fired Australia into an early lead.
But the holder responded well, with the impressive Adrien Rabiot recording a goal and an assist – the latter for Giroud – during a first-half turnaround.
🇫🇷⚽️ GOAL! #FRA gets another in quick succession as @_OlivierGiroud_— beIN SPORTS (@beINSPORTS_AUS) November 22, 2022
fires home to put Les Bleus in the lead!
📺 Follow it LIVE HERE 👉 https://t.co/U1ObSZDUMc #FRAAUS #FIFAWorldCup pic.twitter.com/9IPwclNuOM
Kylian Mbappe then made the points safe with a fine glancing header before teeing up Giroud to nod home his landmark 51st goal as France took control of Group D.
Goodwin side-footed Mathew Leckie's cross into the roof of the net after nine minutes in a dream start for Australia but a quickfire France double turned the game around.
Rabiot contributed to both goals, nodding home Theo Hernandez's deep cross after 27 minutes before his cut-back allowed Giroud to tap in.
The end of an entertaining first half featured clear chances at both ends, with Mbappe firing over from close range before Jackson Irvine headed against the post.
Giroud went close to a spectacular second when he sent an acrobatic effort wide shortly after the break, while Antoine Griezmann saw a shot cleared off the goalline as France continued to press.
France finally had a deserved third goal after 68 minutes, with Mbappe diverting Ousmane Dembele's cross in off the post to clinch the win.
🇫🇷⚽️ GOAL! @KMbappe— beIN SPORTS (@beINSPORTS_AUS) November 22, 2022
was not to be denied this time as #FRA finally capitalises on its chances to make it 3-1 against #AUS
📺 Follow it LIVE HERE 👉 https://t.co/U1ObSZDUMc #FRAAUS #FIFAWorldCup pic.twitter.com/oit1sk9iAn
Mbappe sent in a fine cross for France's fourth just three minutes later, but the moment belonged to Giroud as he powered a header beyond Mathew Ryan to earn a slice of Les Bleus history.
🇫🇷⚽️ GOAL! 👏👏 @_OlivierGiroud_ joins Thierry Henry atop @FrenchTeam's all-time top scorer's list with his second as #FRA takes a 4-1 lead against #AUS— beIN SPORTS (@beINSPORTS_AUS) November 22, 2022
📺 Follow it LIVE HERE 👉 https://t.co/U1ObSZDUMc #FRAAUS #FIFAWorldCup pic.twitter.com/zicUSTfnPJ
🇫🇷🆚🇦🇺 FULL TIME | A bright start for the @Socceroos, but @equipedefrance clicks into gear and gets a big win to start its @FIFAWorldCup defence#FRAAUS #FIFAWorldCup pic.twitter.com/LSIQlkkIuY— beIN SPORTS (@beINSPORTS_AUS) November 22, 2022