A second-half strike from Aaron Mooy proved enough for the Terriers as they claimed a deserved win over a team who finished above them in the Championship last season.
It took just four minutes for Huddersfield to create their first Premier League chance in front of their own supporters, with Mooy's low strike being comfortably kept out by Newcastle stopper Rob Elliot.
While the visitors were holding their own in the early stages, it was Huddersfield who continued to look the most likely to open the scoring with Tom Ince sending a first-time effort straight at Elliot from 20 yards when the former Derby County winger would have perhaps expected to find either corner.
However, Newcastle soon responded and a minute later, Matt Ritchie was only denied a goal when Jonas Lossl pulled off a stunning one-handed save down to his left, with the ball being tipped behind for a corner.
As the first half progressed, chances became few and far between with Huddersfield's intensity being cancelled out by Newcastle's directness, but only a last-gasp challenge from Huddersfield's Christopher Schindler stopped Dwight Gayle from converting from six yards out.
When the teams returned for the second half, there was extra intent to move into the final third, and Huddersfield stunned their opponents with a superb goal five minutes after the restart.
The move was started and finished by Mooy, who played the ball to Elias Kachunga and when receiving it back, the Australian international curled the bar into the far corner from 18 yards out.
From the resulting corner, an opportunity was created for Ayoze Perez from close range, but he somehow sent his volley high over the crossbar.
It soon became apparent that David Wagner had his eyes on seeing the game out rather than pushing for a second goal, and while it appeared to be a dangerous approach with 20 minutes still remaining, it was effective and only Joselu was able to send a tame header towards Lossl's goal.
Joselu had one final volley for the Magpies but after that failed to trouble Lossl, Huddersfield were able to hold on to seal a famous win in front of their own supporters, one which sees them maintain their 100% record alongside Manchester United and West Bromwich Albion.