Harris made the bench for Newcastle's Champions League group game at AC Milan last season.
He told the club's website: “It’s an unbelievable feeling to sign my first professional contract with Newcastle United. It means a lot with it being with my boyhood team as I’ve grown up loving the club and it’s so surreal that I’m officially a professional footballer for the club.
“My footballing journey started seven years ago and it’s been absolutely incredible. I don’t have any regrets and, so far, I’ve made the most of the opportunities I’ve been given. There’s been low points in my career but they’ve taught me more than the highs ever could so I’m grateful for both.
“To make my first-team debut for Newcastle in Australia was something I’ll remember forever. It was a great experience and I learnt a lot from the 30 minutes I played. The whole trip was brilliant and I made a lot of memories along the way. To progress through to the first-team is the long-term goal and it’s one I’ll strive towards non-stop during my time at the Academy and watching goalkeepers such as Tim Krul, Freddie Woodman and Fraser Forster has inspired me to do the same."