The 23-year-old Croatia international, who has penned a four-year contract with the south-coast club, is Mauricio Pochettino's first signing of the summer
The 23-year-old, who is Mauricio Pochettino's first signing this summer, has penned a four-year contract with the south-coast club.
Lyon have confirmed Southampton could also pay up to £1.7m in add-ons for the Croatia international, who made 18 appearances in Ligue 1 last season.
"I’ve spoken a lot with the chairman and the coach, and this is a great project," Lovren told the club's official website.
"They told me a lot of positive things, and I know the history of the club. It’s a big club and I’m very happy that I can be a part of it.
"After three-and-a-half years in France, it was a dream to play in the Premier League. Now the dream has come true.
"I have it in my mind to do something big, and I see the same thing in the club.
"We are a young team, and I am a young player also so I hope I will stay here for a long time."
Pochettino, who guided Southampton to a 14th-placed finish in the Premier League last term, claims it was valuable to complete the deal to sign Lovren before the start of the club's pre-season campaign.
"We are very happy because Dejan is a very good player with good potential," he said.
"In pre-season it’s important to have all players working together, so [Lovren’s signing] is a very good job by the chairman and all of the staff at the club."