The transfer fee has not been disclosed but British media reported Arsenal will pay Chelsea 65 million pounds with an additional 5 million pounds in add-ons.
"It's super exciting for me to be joining this amazing club and to be part of the Arsenal family. This club has such a big history, and I hope we can achieve lots of things," Havertz told the club website.
Havertz joined Chelsea in September 2020 from Bundesliga side Bayer Leverkusen, where he had started his professional career.
"Kai is a player of top quality. He has great versatility and is an intelligent player. He will bring a huge amount of extra strength to our midfield and variety to our play," manager Mikel Arteta said.
Chelsea had paid up to 71 million pounds, including add-ons, for the German forward, according to media reports, making him Chelsea's second-most expensive signing after goalkeeper Kepa Arrizabalaga.
Havertz made nearly 140 appearances for Chelsea in all competitions scoring more than 30 goals, and helped them win the Champions League in 2020-21, as well as the UEFA Super Cup and Club World Club in 2021.
"The German now moves on but leaves with his name etched into Chelsea folklore. We are grateful to Kai for his efforts throughout his time at Stamford Bridge and wish him well," Chelsea said in a statement.
Havertz has played almost 40 times for Germany after making his debut in a 2-1 friendly win over Peru in September 2018.
He was included in their squads for Euro 2020 and the 2022 World Cup, where he scored a brace in a 4–2 win over Costa Rica before Germany were knocked out in the group stage.
