The 24-year-old, with 10 England caps and three England goals, had been
linked with the move for some time.
Press reports suggested a fee of £12million (15.7million euros) had been
Townsend becomes the second England international to join Newcastle in the
transfer window after midfielder Jonjo Shelvey signed from Swansea for £12
million (16 million euros) last Tuesday.
"Bringing Andros to the club is a great signing," Newcastle coach Steve
McClaren told Newcastle's website.
"He loves taking on defenders and crossing the ball. He feels he has a lot to
prove and I can't wait to see him do that in a Newcastle shirt."
Townsend, who made 93 appearances for Spurs, was equally enthusiastic
about his new club, who are currently in the relegation zone, third from
bottom of the league.
"I'm delighted to be here," Townsend, who missed the 2014 World Cup
through injury, told the Newcastle website.
"Newcastle United is a fantastic club with great fans, a great stadium and
great tradition. As soon as I heard Newcastle were interested in me, there
was only one place I wanted to go so I can't wait to get started."
With just 15 games to play, and facing a battle to preserve their top-flight
status, McClaren is in the hunt for further striking reinforcements with Saido
Berahino, Loic Remy and Bafetimbi Gomis reportedly in his sights.