The 22-year-old Tyneside-born academy product, who made his first-team debut in an FA Cup tie at Brighton earlier this year and was handed a full Premier League bow in last weekend's derby defeat at Sunderland, was thrilled to have committed his future to the Magpies.
Dummett, who marked his third senior appearance with his first goal in the 2-2 draw against Liverpool at St James' Park last month, said: "I am delighted to secure my long-term future with Newcastle United.
"Like so many local lads, it has been my boyhood dream to play for this club and now I am looking forward to repaying their faith in me and working hard to be the best possible player I can be."
Dummett played 36 games and won the Scottish League Cup during a loan spell at St Mirren last term, and manager Alan Pardew feels that experience has been a positive for the player.
"Paul fully deserves his new contract and we're delighted for him," Pardew said.
"He has made great progress in the last year, benefiting enormously from his spell at St Mirren last year.
"His performances this season for us have been first class and we were all delighted he scored his first goal for the club against Liverpool, and a very important one at that."
Director of football Joe Kinnear added: "We're delighted that Paul has committed his long term future to the club.
"In reality, this was never in doubt as we wanted Paul to stay and, as a Geordie, Paul made it clear that the only place he wanted to play was Newcastle United - it was just a question of finding the right deal for both parties, which we have managed to do."
- Sports & Recreation
- Newcastle United
- Premier League