The 29-year-old, who missed South Korea's 2-0 win over Germany on Wednesday due to injury, will officially join the Magpies on July 1 when his contract expires at the Liberty Stadium.
Ki puts pen to paper on a two-year-deal at St James' Park and returns to the North East having spent the 2013-14 season at Tyne-Wear rivals Sunderland on loan – helping the club to the Carabao Cup final.
“I’m so pleased” – Ki
The South Korean captain becomes Rafael Benitez’ second summer signing after the goalkeeper Martin Dubravka joined from Sparta Prague, and Ki told NUFC.co.uk: "I’m so pleased I can join the club.”
Ki, who has experienced St James’ Park with Swansea and the Black Cats, admitted he “was always pleasantly surprised” when he visited and believes “there is a great atmosphere and the passion from the fans is a great support to the players.”
He added: "Everyone knows how big this club is so I’m really looking forward to playing with my teammates and for the fans."
“Easy decision” – Benitez
With Mikel Merino nearing the exit door - returning to Spain to join Real Sociedad - his imminent £12 million sale left the Magpies with a void to fill in the central midfielder area.
Benitez, who is rumoured to be working with a limited transfer budget for the second successive season, has acted swiftly - and cheaply – highlighting Ki’s top-flight and international experience as a positive trait.
"I’m pleased to welcome Ki to the club," said the 58-year-old. ”He is a player with lots of Premier League and international experience and it was an easy decision to bring him here.
“He is the captain of his country, a good character and he will be a good addition to the squad."