The 25-year-old signed a long-term contract with the Gunners after having passed a medical on Monday.
Arsenal boss Arsene Wenger told the club’s official website: “We are delighted to have secured the signing of Olivier Giroud.
“He has a very good physical presence and is exceptional in the air, with a great work ethic. We are excited about Olivier joining us and he will add an additional dimension to our attacking options next season.
“He has proved that he is capable of performing at the top level with club and country, and we saw what a big influence he was in Montpellier’s championship-winning side last season.
“We all look forward to Olivier joining us and seeing him play in an Arsenal shirt.”
Giroud scored 21 goals for Montpellier last season.
Giroud added: “I am delighted to be here at Arsenal and to be part of one of the great teams in English football.
“It’s a huge satisfaction to join this great club and it’s been a dream since I was young to play in the Premier League.
“I was attracted by the philosophy of football and Arsene Wenger’s ‘touch’ at this club. I have always admired Arsenal with its great history and reputation, and I now hope to achieve great things here.
“I’m very proud to be a Gunner and I will give my best for all the Arsenal fans.”
