Manchester United have confirmed the signing of Ajax defender Lisandro Martinez in a reported €57million (£48m) deal.
An agreement on the fee was reached between the clubs on July 17, and the player has now signed a five-year deal, with the option of a further year.
The 24-year-old follows former coach Erik ten Hag to Old Trafford in a move that is thought could potentially rise to €67m (£56.5m) with add-ons.
Martinez's arrival marks the latest building block of the Dutchman's restructuring of the English giants, who posted a worst-ever points total in the Premier League era last term (58).
They also conceded the most goals they ever have in a Premier League campaign (57), something Ten Hag will hope the Argentina international can help improve.
Speaking to the club's official website following the announcement, Martinez said: "It's an honor to join this great football club. I've worked so hard to get to this moment and, now that I'm here, I'm going to push myself even further.
"I've been lucky enough to be part of successful teams in my career and that's what I want to continue at Manchester United. There will be a lot of work to get to that moment, but I firmly believe that, under this manager and coaches, and together with my new teammates, we can do it.
"I want to thank Ajax and their fans for all the support they gave me. I had an unbelievable time there but feel the moment is right to test myself in another environment. Now I am at the perfect club to do this."
Martinez follows Tyrell Malacia and Christian Eriksen through the door at Old Trafford, while Ten Hag has also held crunch talks with wantaway forward Cristiano Ronaldo.