The 20-year-old made his first start for the Gunners in a Champions League defeat to Olympiakos last season but left the club in summer.
|18/1||Swansea City are 18/1 with PaddyPower to finish in the Premier League top six
He told Swansea's official wesbite: "I've been at Arsenal since I was 11, so to come to Swansea was the perfect move for me in terms of style.
"Swansea are a growing club and they've come from League Two by passing their way out of the divisions. I think everyone has been very impressed by what they have achieved in the Premier League and it's great to be a part of the club.
"My aim is to start impressing in the Under-21s team and hopefully give Michael Laudrup another option at left-back for the first team. He was a great player and the chance to learn from him is a massive opportunity for me.
"And he is not afraid to give youngsters a chance to prove themselves, either. You only have to look at what Ben Davies achieved last season to realise that."