According to Goal.com, the France international joined the Blues on an 18-month contract with an option to extend it for another year.
Giroud told Chelsea’s official website: ‘Chelsea is one of the biggest teams in the Premier League. They have won maybe the most trophies in the last six or seven years. It’s a massive club and I am proud to sign for Chelsea, and I’m looking forward to playing.’
The 31-year-old had grown frustrated at the Gunners after being dropped to the bench following Alexandre Lacazette’s arrival from Lyon.
Giroud started just one of his 16 Premier League games this season, scoring four goals, and had been linked to West Ham, Everton and Borussia Dortmund in recent months but opted to stay at the Emirates Stadium.