Arsenal have signed England defender Ben White from Brighton in a £50m deal.
White, who was a late call-up to Gareth Southgate's England Euro 2020 squad, has signed a five-year deal with the option of a further year and will wear the No 4 shirt.
Arsenal saw two bids for the 23-year-old rejected before an agreement was reached with Brighton, who have inserted a sell-on clause.
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Arsenal manager Mikel Arteta said: "Ben was a top target for us and it's great that we've completed his signing. Ben has been educated with two very good clubs, Brighton and Leeds, in recent seasons. He has benefitted well from two very good coaching set-ups and has shown with both Brighton and on loan with Leeds what a strong talent he is.
"Ben is an intelligent defender who is very comfortable with the ball at his feet and his style fits perfectly with us. And of course, he is still young, so his age and profile fits with what we are building here. We are all looking forward to Ben being central to our future long-term plans.
White will immediately join up with his new team-mates ahead of the Mind Series friendly match at home to Chelsea on Sunday.
He is the club's third first-team summer signing, after left-back Nuno Tavares joined from Benfica for around £8m and midfielder Albert Sambi Lokonga arrived from Anderlecht.
The centre-back made 39 appearances for Brighton in all competitions last season as the Seagulls finished 16th in the Premier League under Graham Potter.
Prior to his debut season in the Premier League last year, White impressed on loan during Leeds' Championship title-winning side in 2019-20 which led Brighton to secure him on a new four-year contract.
Analysis by Nick Wright
Arsenal's pursuit of Ben White has caused puzzlement among some supporters. For a side with the third-best defensive record in the Premier League last season, wouldn't £50m be better spent elsewhere?
But for Mikel Arteta, like many coaches in the modern game, a central defender's remit is not simply to keep the ball out of his own net. It is to move it upfield as accurately and effectively as possible, and in doing so become the starting point of the team's attacks.
Arteta regards playing out from the back as a key tenet of his philosophy, but progressing the ball from one end of the pitch to the other has been a persistent problem during his tenure - particularly when he has been without David Luiz, whose departure this summer has left a ball-playing void in the heart of Arsenal's defence.