The teenager, who could the Gunners a total of €20m, is expected to provide competition to new signing Mathieu Debuchy, while his arrival also paves the way for Carl Jenkinson to leave the club.
Chambers become the fifth player to leave the Saints this summer, alongside Luke Shaw, Adam Lallana, Rickie Lambert and Dejan Lovren, and Wenger says he is delighted the Englishman has opted to make the move to north London.
