The young defender, a boyhood Blue and Gwladys Street season ticket holder, has agreed a 2½-year deal that would expire in the summer of 2020.
The new terms mark another milestone for the teenager who made his full Everton debut earlier this month in the Europa League win over Apollon Limassol.
“It is a proud moment for me,” the defender told evertonfc.com. “I've grown up as an Evertonian and still am an Evertonian so it's amazing to be a part of it and what the Club wants to do going forward. It's an exciting time to be a player and a fan.
“It's been a crazy couple of months and weeks for me, but it has all fallen nicely into place and I am on cloud nine at the minute and everything is working out well.
“I am learning a lot every day working with Unsy or with the first team. I am picking up things and trying to take it into my own game so I feel as if I am playing better than when I signed my original contract.
“I would love to play in the first team as regularly as possible, push on and get a few more games under my belt and stay here for many years.”