Trippier has won 35 caps for England.
Trippier will be joining the team from Atlante Madrid for £12m plus add-ons.
Eddie Howe was appointed manager of the club in November and the new Saudi owners have yet to sign a player.
Trippier said he was delighted to be joining the club.
Trippier was signed by Howe when he was the boss of Burnley.
Trippier said that he enjoyed his time in Madrid, but when he became aware of the interest from Newcastle United, he knew he wanted to be there.
Trippier had 18 months left on his contract.
The team is second bottom of the league with one win this season.
"I know the demands of the premier league and I know what an amazing club this is with very talented players, so I'm aware of the work ahead of us, but I know what an amazing club this is with very talented players," said Trippier, who joined the club in
I'm excited to start at St James' Park and I can't wait to play.
Howe said they didn't hesitate when the opportunity arose to secure Trippier.
A lot of hard work has gone into planning for the January transfer window, which is clear in how quickly we have been able to complete this move.
More to come.
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