Financial details of the deal were not disclosed but British media reported Arsenal paid around 27 million pounds ($36.29 million) for the 22-year-old.
Gabriel made 34 appearances in all competitions for Lille last season as they finished fourth in Ligue 1.
"So many fans were sending me messages asking me to join Arsenal and that played a big part in me signing for this club," Gabriel told, “It was a very surreal experience, there were offers coming from a few different clubs".
“I spoke a lot with my family and my agents, I also spoke with some of Lille’s directors, but as I said, this club’s history and traditions and the team project for the next few years were very motivational for my decision to come here.”
Gabriel is Arsenal’s second major signing in the close-season following the arrival of compatriot Willian on a free transfer last month.