The 26-year-old has joined the Premier League club for a reported £52m, which makes him the most expensive player that the Gunners have acquired.
Lacazette, who has penned a long-term deal, arrives at the North London outfit with an impressive scoring record having found the back of the net 129 times in 275 appearances for Lyon.
The prolific forward was initially due to join Atletico Madrid, but the Spanish club's transfer ban caused the deal to collapse, which paved the way for Arsenal to swoop in.
Lacazette, who is believed to have undergone a medical earlier this week, will travel to Sydney with his new teammates this weekend for the club's pre-season tour.
The forward's arrival is Arsenal's second signing of the summer so far following the capture of Sead Kolasinac from Schalke.