Manchester United have competed the €17million signing of Alex Telles from Porto.
The 27-year old left-back has signed until 2024 at Old Trafford, with the option of a further year.
United boss Ole Gunnar Solskjaer said Telles is the kind of character he wants at the club, "He is a player we have been tracking for some time and his performances over the past few years are exactly what we are looking for.
"He is a fighter and a winner and will add real determination and competition to the squad."
His arrival is the first, but unlikely the last of a hectic transfer deadline day in the red half of Manchester.
United are also set to confirm the signing of former Paris Saint-Germain and Palermo striker Edinson Cavani on a two-year deal.
€30million will be spent on Atalanta winger Amad Traore, but the 18-year old is unlikely to arrive until January.
And having missed out on their primary transfer target - Jadon Sancho - the club have been nosing out deals for Watford's Ismaila Sarr, and Barcelona's Ousmane Dembele.
Watford reportedly rejected an initial loan offer from United with the option to buy for £25million (€27.5), but the Championship side value the Ivorian at £45million and are interested only in a permanent deal.
Dembele did not train with his Barcelona teammates on Monday, arriving at their facilities but leaving shortly afterwards.
His manager Ronald Koeman would like to ship Dembele out the door at the Camp Nou to facilitate a move for Memphis Depay from Lyon.
"We want Memphis Depay to come to Barcelona, and Memphis wants to join," Koeman said on Monday, "But a player would have to leave first before we can sign him. But it’s clear that we want him."
Chris Smalling looks likely to leave before the window closes. A permanent move to Roma is in the works, worth €15million plus a potential €5million in add-ons.
