Giroud got gloved up for the Rossoneri following a red card for goalkeeper Mike Maignan after 97 minutes and the France forward made a brave stop to deny George Puscas.
That came in a frantic finale which also saw Genoa goalkeeper Josep Martinez sent off and secured a win which sent AC Milan to the top of the table above city rivals Inter.
There were big celebrations after the final whistle and AC Milan have now decided to mark the Frenchman's heroics by adding him to their squad list as a goalkeeper and also by selling customised jerseys with his name on the back.
"Last night Olivier Giroud became part of Milan history by courageously defending the AC Milan goal in the final minutes of the Rossoneri’s match against Genoa," the club said in a press release on Sunday.
AC Milan have included Olivier Giroud among the goalkeepers on their official squad list following the striker's heroic save vs Genoa on Saturday.Fans can also buy the goalkeeper jersey with 'Giroud 9' on the back at AC Milan stores and on their website. pic.twitter.com/f167dcEKZGOctober 8, 2023
"The Club has decided to honour his performance in its last line of defence by putting him in the list of goalkeepers.
"Additionally, fans can now purchase the goalkeeper jersey and customize it with 'Giroud 9' at AC Milan retail outlets and on the official website."
Milan's winning goal against Genoa also arrived late on, with former Chelsea attacker Christian Pulisic netting the game's only goal after 87 minutes on Saturday.
The Rossoneri are top of Serie A with 21 points, having won seven of their eight matches in the competition so far this season.
City rivals Inter are two points back in second, with Juventus four behind in third place ahead of the international break.
More Serie A stories
Napoli striker Victor Osimhen could be in for a January exit after he was mocked in a video online by his own club.
AC Milan have announced plans to move away from their iconic San Siro home and build a new stadium in the south of the city.
And Roma's Romelu Lukaku is being targeted by fans of former club Inter, who plan to hand out 50,000 whistles to show their 'disgust' when he returns to the San Siro with his current club at the end of this month.
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