Giroud's compatriot Alexandre Lacazette marked his league debut with a goal in just 94 seconds, only for Shinji Okazaki to level for the Foxes less than three minutes later.
Jamie Vardy then capitalised on very bad defending to twice put the Foxes ahead either side of Danny Welbeck's equaliser before Arsene Wenger sent for the cavalry. Substitutes: Olivier Giroud (for Holding, 67) 7, Aaron Ramsey (for Elneny, 67) 7, Theo Walcott (for Welbeck, 75) 6.
The 30-year-old goal machine spent much of the game in the dug out, but came on for Rob Holding in the 67th minute of the game, where he went on to score in the final moments of the game to secure a 4-3 victory for the Gunners.
"It is fantastic", Wenger replied when asked about Giroud's willingness to fight for his place.
"But I don't want him to go and in the end he made a decision to stay and it was one of the days of recent weeks for me because I know how important he is".
"I don't know whether it was a lack of concentration or just a lack of game management in the last ten minutes, but you then concede again from a set play in terms of being overpowered". He's a fantastic player, but as well he has a big weight in this squad.
Arsene Wenger has given an update on the potential transfer of Riyad Mahrez from Leicester and claimed that the Gunners were never close to signing the Algerian (via The Mirror).
He added: "We started really well and I thought we could stay in control".
"I feel as well that the goals we conceded, we can work together to get rid of that because one was a ball we lost in the build-up and we conceded two goals on corners".
Giroud header seals Arsenal win
Shakespeare was true to his word and started Riyad Mahrez despite the Algeria worldwide asking to leave the King Power Stadium. But I don't want him to go and in the end he made a decision to stay. "It was one of the great days".
FTSE ends down as shares hit by US-North Korea tensions
Earlier, the dollar slipped as low as 108.91 yen, its weakest level since June 14, when the greenback fell as low as 108.81 yen. European markets closed lower: London's FTSE lost 0.6 per cent, Paris fell 1.4 per cent and Frankfurt dipped 1.1 per cent.
We held our own against Real: Mourinho
Real Madrid would not sell Cristiano Ronaldo for "his weight in gold", insists club president Florentio Perez. There is a difference of quality. "With Zizou, you already know my opinion of him.