The South coast side had no answer to the high-pressure play of David Wagner’s pumped-up team and finished with 10 men after the second-half sending off of centre-back Lewis Dunk.
This was only a fourth league defeat of the season for Brighton, who had conceded just 18 goals in 27 games on arriving at the John Smith’s.
This was a fine performance lapped up by the home fans in a 20,104 recorded gate (776 visiting fans) and set the stage perfectly for Sunday’s big home derby with Leeds United.
It was Town’s retro game, with fans urged to wear old club shirts from down the ages, and the home side were aiming to turn the clock back to 2010/11, the last season in which they beat Brighton.
The eagerly-anticipated Sky-televised clash pitted two of the Championship’s in-form teams, Town having taken 19 of the previous 24 points available and their visitors 21.
Town made nine changes from the side which put Rochdale out of the FA Cup, with only Elias Kachunga and Izzy Brown remaining, but there was only one difference from the last Championship match, in which Ipswich Town were seen off at the John Smith’s Stadium.
Aaron Mooy missed that match with a back injury, but was a pleasing presence against Brighton, resuming what has been an effective midfield partnership with Jonathan Hogg.
Brighton defender and captain Bruno returned after missing three games with a groin problem, while the Seagulls also featured former Town midfielder Oliver Norwood.
Less than 30 seconds had gone when Bruno was booked for bringing down Rajiv van La Parra as Town made a stirring start, which continued when Tommy Smith picked out Brown, whose low shot was smothered by David Stockdale.
The home side then forced a couple of corners, with van La Parra hitting the outside of the left-hand post from the first of Mooy’s deliveries.
Town had really hit the ground running, and this powerful start was rewarded with a ninth-minute opener by Smith, who shot home after being teed up by van La Parra.
Brighton finally forced an attack after 13 minutes, but keeper Danny Ward was commanding as he punched away Anthony Knockaert’s free-kick, with an offside flag up.
While the tempo dropped a touch, Town were still on top, so it was a huge disappointment when the visitors forced a 20th-minute leveller as Hemed pounced on a weak back header by Mooy, rounded Ward and rolled the ball home.
Centre-back Lewis Dunk’s block thwarted van La Parra as Town sought a quick response, then Michael Hefele headed over from another Mooy corner before Nahki Wells put a 25-yard free-kick into the Brighton wall.
Stockdale did well to deny the lively van La Parra when he took aim with a low shot after a corner was only cleared to the edge of the area, but the Leeds-born keeper was powerless to prevent Wells putting Town back in front after 36 minutes.
A number of players were involved in the build-up, and the former Bradford City ace produced a classy rising finish from inside the area to register his 100th goal in the English game.
Dunk became the second Brighton player to be shown a yellow card by referee James Linington when he fouled Brown after 39 minutes while Glenn Murray was well over from the edge of the area just before the break.
Murray headed home from Norwood’s free-kick only to be flagged offside, then in first-half stoppage time, Town claimed a third, Kachunga heading in from close range after Stockdale pushed a Wells cross up into the air.
Kachunga had only just been booked for a foul on Beram Kayal, but that couldn’t take the gloss off an excellent first half by the hosts.
Van La Parra was only just wide with a curler from outside the area, then after Brown’s close-range shot was blocked, the Dutch wideman brought another good save from Stockdale after a darting run.
Having replaced Kayal with Steve Sidwell at half-time, Brighton made a double change on 62 minutes, with Solly March and new Arsenal loanee Chuba Akpom coming on for Jamie Murphy and Tomer Hemed.
But within four minutes, the South coast side were down to 10 men, with Duffy sent off when his late tackle on Brown was deemed a second caution. Brown was soon replaced by fellow Chelsea loanee Kasey Palmer.
Joe Lolley replaced the excellent van La Parra and Mooy hit a post before Collin Quaner got a home debut.
What a match to remember!