Pinnington has penned his deal after turning 17, having initially joined from Luton Town at 14 years of age.
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"It feels great to sign my first professional contract," the Harpenden-born youngster told newcastleunited.com. "It's been something I've wanted to do since I've been really young so I'm very happy to sign it, especially with Newcastle.
"The club has got great staff, facilities and I like the journey that the club is going on at the moment.
"I've been here since 14 and they've helped me in so many ways, especially after moving up away from home so I didn't want to go anywhere else."