The 33-year-old joined Chelsea in 2004 and went on to play over 450 games at Stamford Bridge.
In his time there he won the Premier League title, the FA Cup (both four times), the Champions League and the Europa League.
Cech was number one at Chelsea for 11 seasons before losing his place to Thibaut Courtois last term, as a result the Czech international only played six league games.
Speaking about his new signing, Arsenal manager Arsene Wenger said: “Petr Cech is a player I have admired for a long time and I am very pleased that he has decided to join us.”
Cech, who signed a four-year deal and cost a reported £10million, added: “When Arsene Wenger spoke to me about his ambitions for this club, and how he saw me as part of this team, the decision was clear.”
Cech has posted an open letter to Chelsea fans on Twitter thanking them for supporting him throughout his time at the club but explained that it was “time to begin a new adventure”.
Arsenal players are delighted that Cech has joined them, Theo Walcott and Aaron Ramsey posted the following on Twitter:
Arsenal fans, is Cech the man that will help bring you the Premier League title for the first time in 11 years? Let us know in the comments section.