Craig Goodwin provided an early scare for Didier Deschamps' side, he smashed the opener into the roof of the net from close range.
The two combined again just three minutes later as Giroud became France's joint record goalscorer after Mbappe darted in from the left-hand side.
Here are four things we learnt from the game.
Mbappe proves his worth
The 23-year-old put in a mature, yet productive performance as his nation eventually brushed aside the Aussies.
Starting on the left, Mbappe's pace caused Nathan Atkinson problems all night as he constantly exploited the space in behind the right-back.
His end product is something that the youngster is often questioned for, but he had no trouble delivering goal contributions in this one.
The cross for Giroud's second was a perfect example of wing play, as the Frenchman showed explosive pace to create space to deliver.
And that is exactly what he did, putting an inviting cross into the box which was met by the towering forward.
But Mbappe's goal showed a slightly different side to him, as he headed home France's third in style.
A typical poachers finish, the forward found space between the two central defenders and was given an inviting ball in to attack from the opposite flank.
Australia fall short after an impressive start
The same looked set to happen until France's second-half transformation.
Although they were let off by some poor finishing during the part of the game that they were leading for, the Socceroos still deserve credit for the way they played in the first period.
Graham Arnold's side limited space well throughout the first half an hour and managed the overloads between the lines adequately with their rigid 4-5-1 formation.
But quality was telling, as they struggled to deal with the threat of Mbappe and Ousmane Dembele in the wide areas during the second half.
Deschamps throws the shackles off (sort of)
The World Cup winning coach has always been notoriously cautious when guiding Les Bleus through international competitions.
And the clash with the Socceroos looked to be the exact type of banana skin fixture that would down Deschamps' men in the past.
Barring the early scare, France looked more fluid in attack and thrived on their attacking overloads.
Starting Mbappe, Giroud, Dembele and Antoine Griezmann was a largely attacking gamble from the boss - which certainly paid off.
The left side was also prominent in their attacking patterns of play, with Lucas Hernandez's early injury forcing Deschamps to bring in the slightly more attacking Hernandez brother in Theo.
It was the combination of Hernandez and Mbappe that became a fruitful source of creation throughout the game.
Deschamps should continue to be adventurous with his team selection in games they expect to win in order to avoid slipping up.
Giroud equals Henry's record
The target man would have been hoping for a brace heading into the group opener in order to equal Henry's all-time goalscoring record.
And that is exactly what he did, his first a smart finish after Rabiot had opened up space inside the penalty area.
The second was a typical Giroud header that he had no right to win following a Mbappe cross.
At 36 years old this could well be his last World Cup and to sign off in style by beating Henry's record would be ideal.