A product of the Newcastle academy, Miley became the club's youngest ever debutant in the Premier League after coming off the bench against Chelsea in 2023.
The midfielder has since made 80 first-team appearances for the club and recorded 14 goal involvements, while even scoring in a 2-2 draw against Bayer Leverkusen in the Champions League.
Miley featured 34 times during the 2025/26 campaign and has now reacted to signing a six-year contract.
"I'm really pleased to sign this new contract and commit my future here. It's a dream to be representing Newcastle United, so this is a proud moment for me," the 20-year-old said.
“I'm really grateful to everybody who has played a part in helping me get to where I am today, especially the support of my family and the trust that the club has put in me from such a young age.
“It's been an amazing journey so far and I'm so excited for what's ahead. I'm now working hard every day to get back on the pitch."
The youngster missed the final three matches after fracturing his fibula in training and his rehabilitation will continue over the summer ahead of a return.