London - Southampton signed Netherlands defender Wesley Hoedt from Lazio for a reported £15 million on Tuesday.
Hoedt agreed a five-year deal with the Premier League club and will arrive at St Mary's as a potential replacement for his compatriot Virgil van Dijk.
Van Dijk is a target for Liverpool and Chelsea, but Saints insists he will not be sold, even though the central defender has still not joined first-team training under new manager Mauricio Pellegrino.
Hoedt began his career at AZ Alkmaar in his home country before moving to Lazio in 2015.
The 23-year-old, who made his senior international debut earlier this year, can't wait to get started in the Premier League.
"I'm really happy to be here. I think Southampton is a really big club, so it's a good next step for me to come here and to play in the Premier League and try to help the best I can," Hoedt told Saints' website.
Hoedt is Southampton's third signing since last season after the arrivals of midfielder Mario Lemina and defender Jan Bednarek.