Southampton have signed Netherlands centre-back Wesley Hoedt from Lazio for £15m on a five-year deal.
Hoedt, 23, joined the Serie A side from AZ Alkmaar in 2015 and made his full international debut earlier this year.
Saints vice-chairman Les Reed said Hoedt is "one of the most promising young defenders in Europe".
His Dutch team-mate and Saints captain Virgil van Dijk recently handed in a transfer request, but the club say he is not for sale.
Reed added: "Wesley has proven his talent through his performances for Lazio, as well as the Netherlands, and we believe he can develop even further here at Southampton, alongside his international team-mate Van Dijk, as well as the likes of Jack Stephens, Maya Yoshida, Jan Bednarek and Florin Gardos."
He is Saints' third summer signing after the arrivals of midfielder Mario Lemina for a club record £18.1m and defender Jan Bednarek for £5m.
Hoedt said: "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."
Find all the latest football transfers on our dedicated page.