On the news, Arsenal’s technical director Edu said: “We are delighted to have signed Gabriel.
“He is a player we have been studying for a while and he was in demand from many clubs, so we are proud to have agreed and completed this transfer with Lille and the player.
“Gabriel is a player of high quality and Mikel and his coaches are looking forward to integrating him into the club.”
Gunners head coach Mikel Arteta added: “We welcome Gabriel to Arsenal. He has many qualities which will make us stronger as a defensive unit and as a team.
“He has proved with Lille that he is a defender with many outstanding attributes and we are looking forward to watching him grow as an Arsenal player.”