Gabriel Magalhaes will wear the No6 shirt at Arsenal after completing his move from Lille.
The Gunners unveilled their new signing on Tuesday afternoon with fellow Brazil internationals David Luiz and Willian doing the honours via the club's Facebook page.
The defender has signed a five-year deal with the club, arriving for a fee believed to be around £26million.
He takes the squad number previously worn by former Arsenal captain Laurent Koscielny, who left the club last summer. Club greats Tony Adams and Steve Bould also took no6.
Gabriel told Arsenal Digital: "So many fans were sending me messages asking me to join Arsenal, and that played a big part in me signing for this club.
"I know the history and traditions of this club and it is a pleasure being here. I am very happy and hope I can contribute to many titles with the Arsenal shirt."
