The long-serving Poland international confirmed after the FA Cup final he was set to leave the Gunners and will complete a move to the Welsh club when his current contract expires
As revealed by Goal, the Polish shot-stopper rejected a last-ditch attempt by the north Londoners to prevent him from leaving the club, and has now opted to join the Welsh outfit.
"Everyone at Arsenal would like to thank Lukasz for his contribution to the Club and to wish him well for his future career," read a statement on Arsenal's official website.
The 29-year-old joined Arsenal from Legia Warsaw in 2007 and made a total of 78 first team appearances for the club in all competitions.
Despite a series of impressive performances during Arsenal's successful FA Cup campaign this season, Fabianski, who saved two penalties in the semi-final shootout win over Wigan, never threatened to usurp his Polish compatriot Wojciech Szczesny as Arsene Wenger's first choice goalkeeper.
Having been forced to play second fiddle to the likes of Jens Lehmann, Manuel Almunia and Szczesny during his Arsenal career, Fabianski admitted after the Wembley win over Hull earlier this month that he would be leaving the club in search of regular first team football.
He said: "It was probably my last game for Arsenal. I don't know what I can say, but if I end my Arsenal career in that way then it is the best way to finish."
Fabianski, who has 21 caps for his country, will provide competition for Michel Vorm and Gerhard Tremmel who are all vying to become Gary Monk’s first-choice keeper at the Liberty Stadium.
Arsenal, meanwhile, will need to seek experienced goalkeeping cover for Szczesny with Fabianski departed and Emiliano Viviano, who failed to make a single first team appearance last season and is unlikely to make his move permanent after he joined on loan from Parlermo.