British media reported that the fee for the 26-year-old was a club record 46.5 million pounds ($60 million), surpassing the 42.4 million pounds Arsenal paid Real Madrid for Germany midfielder Mesut Ozil in 2013.
“We are very happy to have Alexandre join our group," Arsenal manager Arsene Wenger told the club website (www.arsenal.com).
"He has shown over a number of years that he can score goals and that he is a very efficient finisher. As well, he has very interesting technical qualities and a strong character.
"He is a guy who is a great addition for us, and someone who will help us challenge at the top level this season."
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Lacazette, who has won 11 caps for France, has scored at least 20 league goals in each of the last three seasons and managed 37 goals in 45 games last season as Lyon finished fourth in Ligue 1 and reached the Europa League semi-finals.
He becomes Arsenal's second major signing of the close season, following the arrival of Bosnia defender Sead Kolasinac on a free transfer from Schalke 04.
The arrival of Lacazette will be a boost for the Gunners, who won the FA Cup last season but only finished fifth in the Premier League, meaning that this season they will miss out on the Champions League for the first time in 20 years.
(Reporting by Ed Osmond; additional reporting by Aditi Prakash in Bengaluru, editing by Julian Shea)
