The 19-year-old made his Premier League debut for the Saints on the opening day of the 2013/14 campaign, going on to feature 22 times in the competition last term.
Chambers joined the Southampton academy aged seven, breaking into the club’s first team squad at the beginning of 2012/13.
Tall and athletic, the versatile youngster started his career in midfield, but established himself at right back last season and can also play in the centre of defence. He is currently captain of England Under-19s.
Arsène Wenger said: “We are very pleased that Calum has agreed to join us. The way he adapted to the Premier League last season with Southampton at a young age shows that he has tremendous quality. He has a lot of the attributes that we look for in a young player and I am sure that he will do well with us.”
Chambers said: “I am so happy to be signing for Arsenal. They are a team I have much admired for their playing style, and a team who have been one of the top sides in Europe for many years. I’m looking forward to joining up with my new team-mates today and beginning preparation for the season ahead.
“I would like to take this opportunity to say thank you to everyone at Southampton FC for everything they have done for me and for making this move possible.”
It is expected that Chambers will make his first Arsenal appearance at the Emirates Cup 2014, which takes place at Emirates Stadium on August 2 and 3.
Chambers’ Arsenal squad number will be revealed soon through Arsenal’s official Instagram account.
-Story and picture from Arsenal.com