Goals from Jamaal Lascelles and Jonjo Shelvey earned the Magpies a deserved three points from the Sky Bet Championship fixture, while putting an end to the Seagulls' unbeaten start to the 2016/17 campaign.
Captain Lascelles broke the deadlock early on, losing his marker to connect with Matt Ritchie's free-kick and power home an impressive header.
Yoan Gouffran twice went close to doubling that lead - including sending a stunning long-range effort against the crossbar - while Ritchie also threatened for the outstanding hosts before half-time.
United's task was made easier at the start of the second period when Albion forward Sam Baldock was dismissed for a second booking, after fouls on Ayoze Perez and goalkeeper Matz Sels.
And Newcastle made the most of their numerical advantage almost immediately, as Jonjo Shelvey bent in a 25-yard free-kick for his first goal for the Club
Manager Rafa Benitez will be delighted with his side's performance in their final game before the international break, and they will look to extend their winning run when they travel to Derby County on Saturday, 10th September.
Previously-unbeaten Brighton made a bright start to proceedings and threatened inside the opening three minutes.
Jiri Skalak's inswinging free-kick was met by Glenn Murray but the big striker, who had crept into an offside position and was rightly flagged, was denied by an outstanding point-blank save from Matz Sels.
However, Newcastle grew into the contest and broke the deadlock in the 15th minute through Lascelles.
Jonjo Shelvey had been fouled around 30 yards out and when Ritchie delivered the resulting free-kick, the Magpies' skipper lost is man to thump home a brilliant header.
United were in full flow, roared on by a vociferous St. James' Park crowd, and in the 23rd minute, Gouffran came within inches of his first goal since January 2015, which would have doubled the hosts' advantage.
Picking up the ball wide on the left, the French winger proceeded to nutmeg Anthony Knockeart, drive inside and send a 25-yard effort crashing against the crossbar with Albion keeper David Stockdale completely beaten.
Ritchie was next to try his luck but saw his right-footed shot beaten away by Stockdale after Mohamed Diame had cut-back into his path.
It was one-way traffic and, from the resulting corner, Gouffran fired a half-volley narrowly over the top, when a well-worked short corner had been lofted into his path by Vurnon Anita.
A rare Seagulls attack just past the half hour mark forced Sels into action, with the Belgian stopper doing well to parry Baldock's dangerous close-range strike.
After a lively first period, the opening exchanges of the second half certainly followed suit, with a chance at either end and a red card.
First, Gouffran volleyed Anita's right-wing cross high over the bar before, at the other end, Knockaert clipped the top of the crossbar after Beram Kayal had tricked his way into the box.
And then, in the 55th minute, Albion were reduced to ten men. Baldock, booked on the stroke of half-time for a cynical trip on Perez, caught Sels as the goalkeeper went to clear, and referee Keith Stroud produced a second yellow card for the former MK Dons striker.
United doubled their advantage just past the hour-mark - Shelvey curling home a brilliant 25-yard free-kick at the Leazes End which left Stockdale static. It was the midfielder's first goal for the Club and fully deserved after asome excellent performances of late.
Clearly buoyed by that, minutes later he almost had his second, as Shelvey picked up the ball in space, raced forwards and unleashed an angled left-footed effort that was on its way into the far corner until the intervention of Stockdale's fingertips.
Despite being a man down, Brighton threw everything at the home side in the closing stages, and applied some heavy pressure with a number of dangerous balls into the box.
But, led by exceptional captain Lascelles, the Magpies held firm to record their third clean sheet in a row.
