London - Newcastle landed Feyenoord defender Daryl Janmaat as an immediate replacement for Mathieu Debuchy following the French right-back's move to Arsenal on Thursday.
Netherlands international Janmaat is reported to have cost £6 million, with the official announcement of his arrival at the Premier League club timed to coincide with Debuchy's departure.
The 24-year-old, who underwent a medical on Tyneside earlier this week, has signed a six-year contract and will replace Debuchy as the club's first-choice right-back.
Janmaat, who has just returned from the World Cup finals in Brazil, said: "Newcastle is a fantastic club, with a big history and a great stadium. I have also been told all about how great the fans are.
"This is the perfect move for me, and I am really looking forward to being with the team and getting started here at Newcastle. I think we are going to have a great season."
Magpies boss Alan Pardew added: "He is the perfect example of a modern full-back: someone who is good defensively, but offers a real threat going forward as well.
"Daryl had an excellent World Cup and we are looking forward to him continuing that form for Newcastle."
Janmaat becomes Newcastle's sixth close-season signing, with owner Mike Ashley having handed Pardew the financial backing to carry out a major overhaul of his squad.
He is the third new arrival this week following Montpellier midfielder Remy Cabella and Monaco striker Emmanuel Riviere, and he is unlikely to be the last with the capture of another frontman a priority.
Janmaat, like Cabella, will not travel with the Newcastle squad on a week-long trip to New Zealand as he enjoys an extended break after his exertions in Brazil.