The Gunners were on the hunt for a number two goalkeeper after allowing Emiliano Martinez to join Aston Villa in a £17m deal.
Speaking to the club's official website after announcing the signing, manager Mikel Arteta said: “We want to create healthy competition for places and we look forward to seeing Alex bring further depth to the goalkeeping position.”
Technical director Edu added: “We’re very pleased to welcome Alex to our squad. We have been monitoring him for some time and from the analysis, he has strong attributes that we look for in a goalkeeper and as a person.”
More to follow.