Timothy Fosu-Mensah has joined Bayer Leverkusen from Manchester United on a three-and-a-half-year deal.
The versatile 23-year-old has moved to the Bundesliga side for a fee in the region of €2million (£1.8m).
Leverkusen sporting director described their new signing as "a technically adept, fast and physically strong defender, who can be used both as a right-back and in the middle".
Fosu-Mensah, who has three senior caps for the Netherlands, said: "In the past few days, I've talked a lot with the coach [Peter Bosz], and conversations with Simon Rolfes and Rudi Voller have convinced me there are big prospects at Leverkusen, both for me personally and the team.
"It's going to be really exciting."
Fosu-Mensah joined United's academy in 2014, having spent eight years in the Ajax youth set-up, and went on to make 30 senior appearances in all competitions.
He signed a four-year deal in October 2016, with the option of an extra year, after making his senior debut in February that year under manager Louis van Gaal, playing as a makeshift left-back in a 3-2 Premier League win over Arsenal.
He spent time on loan with Crystal Palace and Fulham but his opportunities in England were curtailed by serious injuries, and his place in Ole Gunnar Solskjaer's squad was usurped by fellow academy graduate Brandon Williams.
Although he was offered a new contract, he reportedly rejected the terms as he felt undervalued by the offer and was keen to move elsewhere to maximise his potential, leaving United keen to sell in January and avoid losing him for nothing at the end of the season.
While Fosu-Mensah departed on Wednesday, new signing Amad Diallo was at the club's training complex for the first time.
The 18-year-old arrived from Atalanta this month after a deal was struck between the clubs in October.