The 19-year-old has joined Arsenal from Bundesliga side Hertha Berlin. Omar is a ball playing centre half who can play on both sides.
Omar was born in the Netherlands and he has played internationally at youth level for Tunisia and the Netherlands. Throughout his youth career he also spent time at Feyenoord, Manchester City, PSV Eindhoven and Marseille.
Everyone at Arsenal welcomes Omar to the club and they look forward to supporting his ongoing development.
This contract is subject to the completion of regulatory processes.