Newcastle announced on Friday they had signed Kieran Trippier from Atletico Madrid, with the England international becoming the first arrival under the club's new Saudi-led ownership.
The 31-year-old full-back has moved back to the Premier League for an undisclosed fee, understood to be in the region of £12 million ($16 million) plus add-ons.
The former Tottenham defender has signed a two-and-a-half-year contract and his arrival signals the launch of a new era under Eddie Howe, who was appointed as manager in November.
"Newcastle United are delighted to confirm the signing of England full-back Kieran Trippier from Atletico Madrid for an undisclosed fee," the club said in a statement.
"The 31-year-old has agreed terms on a two-and-a-half-year deal and becomes the first senior signing under the club's owners and head coach Eddie Howe."
Trippier said he was relishing his return to England from Spain.
He said: "I'm delighted to be joining this fantastic club. I really enjoyed my time in Madrid, but when I became aware of interest from Newcastle United, and having worked with Eddie Howe before, I knew this was where I wanted to be.
"I'm aware there is a lot of work ahead of us, but I know the demands of Premier League well and I know what an amazing club this is with very talented players. I can't wait to get started."
Newcastle face a struggle just to stay in the Premier League. They are just one place off the foot of the table after a single win all season.