The Spurs U21 captain has moved to the Magpies on a season-long loan.
Director Richard Montague told the club's website: “We’re really excited to welcome a young player of George’s calibre.
“He’s incredibly well thought of at Spurs, as reflected by their decision to give him a new three-year deal this summer.
“George also has a growing reputation at international level, having represented England’s Under 19s and 18s.
“His natural position is defensive midfield, but he’s also comfortable at full-back or in central defence. He gives us real strength in depth in several areas and, as well as tremendous quality in possession, he brings athleticism and a determination to succeed in his first full season in men’s football.
“We’re really pleased to have the opportunity to contribute to his development and have every confidence he will make a big impact in his time with us.”