The sought-after 21-year-old Ghanaian has signed a four-year contract at St Mary’s, becoming the second player to arrive at the club during this year’s summer transfer window.
One of the most highly-regarded young centre backs playing in Europe right now, Salisu moved to Spanish top-flight side Valladolid from his homeland in 2017, first establishing himself in their second side, before quickly progressing into a key member of the first-team.
Salisu featured twice in the club’s Copa del Rey campaign in the 2018/19 season before becoming a regular in the 2019/20 campaign, making 32 appearances across all competitions, helping them to a notable improvement in their defensive record and also to a respectable 13th-placed finish.
Southampton manager Ralph Hasenhüttl said: “This is an important signing for us. Mohammed is a player who fits our profile well. He is young and has a great amount of potential, but he is also someone who has the qualities to come in and help the team as soon as he is up to speed with our way of playing.
“I like what I have seen of him so far in his games with Valladolid. He is strong defensively, he is calm with the ball – something that is important in our team – and he has good speed too.
“I think he will fit in well with us and that this will be a good place for him to develop his game further. We have some good centre-backs here and this will be another strong option for us.”
Mohammed Salisu said: “It is a very good feeling to be a Southampton player. I am very happy to be part of the club and I am looking forward to starting here.
“Southampton is a club with a very rich history in developing young players, so it is a very good club for me to develop my skills and to learn a lot as a young player.
“I know that the team expects a lot from me and I’m going to try to give all I can to help the team.”