Newcastle completed the signing of defender Tino Livramento from Southampton on Tuesday for a reported initial fee of £32 million ($41 million).
Livramento, 20, impressed during the 2021/22 season shortly after moving to St. Mary's from Chelsea.
However, he missed most of last season due to an anterior cruciate ligament injury sustained in April 2022 as Southampton were relegated from the Premier League.
The BBC said the total fee could rise to £40 million should performance-related bonuses be met.
Newcastle boss Eddie Howe has now added three new players to his squad during the transfer window following the arrivals of Italian international midfielder Sandro Tonali and winger Harvey Barnes.
"At 20, he already has lots of attributes that I admire but he also has the potential and drive to really grow with this team," said Howe in a club statement.
"I'm looking forward to working with him and to seeing him develop in a Newcastle shirt."
Backed by the Saudi sovereign wealth fund, Newcastle have qualified for the Champions League for the first time in 20 years.
Livramento, who has signed a five-year contract, said the Magpies' upward curve played a major role in attracting him to St. James' Park.
"The way the manager plays football is really attractive and I feel like it suits me as a player," said the England under-21 international.
"With how well the team did last season, the trajectory that we're on now, I'm just looking forward to being a part of that."
Newcastle begin their Premier League campaign at home to Aston Villa on Saturday.
