Goals from Rodrigo, Harrison and Aaronson gave Leeds the bragging rights at Elland Road.
Chelsea saw Red in the game, with new signing, Kalidou Koulibaly, getting sent off late on.
The result will leave Chelsea Coach, Thomas Tuchel, pondering on how it all went wrong.
For the host, Manager, Jesse March, will most likely let the champagne flow in celebration after a truly inspired performance as they remain unbeaten this season.
As early as the 1st minute, Gallagher played in Raheem Sterling who dribbled before releasing a shot that went narrowly wide.
From then on, Leeds played an impressive high press, harrying Chelsea players and giving them no time on the ball.
Rodrigo tried to catch Mendy unawares in the 20th minute but just dragged his shot wide from the far left edge of the box.
Mount had a shot saved by Melee in the 22nd after Chelsea successfully played out from the back this time.
Disaster then struck for Chelsea in the 33rd minute as Mendy’s attempt to dribble out from the back was cut out by Brendan Aaronson who stole the ball and strolled into the net for Leeds’ opener.
Rodrigo made it two for the hosts when, in the 37th minute, he nodded in from a freekick Sterling had earlier conceded.
Leeds were sailing by now as they seemed comfortable in possession, but Cucurella should have done better when a well worked ball from Loftus Cheek fell kindly for him only to shoot well wide with the goal in sight in the 40th.
With just seconds left to the end of the game, Koulibaly played a lofted ball into the box which Mount failed to gather else, he would have been one v one against the Leeds goalie.
The first-half ended with Leeds going into the break with a shock 2-0 lead.
At the start of the second half, one would have thought Chelsea will come flying out of the box, but, kudos to Leeds who had their tactics spot on as the continued just as the first half ended.
Leeds kept pushing, surprisingly and Loftus Cheek had to track back in the 56th to stop Harrison from pulling the trigger in the box.
Tuchel had to respond at this stage and did so with a double change in the 63rd minute with Pulisic and Ziyech replacing Jorginho and Gallagher.
All that didn’t matter, though, as Leeds hit Chelsea for three in the 69th minute.
Jack Harrison was the man on target this time as he reacted quickest in the box from a cross to tuck the ball in.
Chilwell came in for Mount in the 78th minute to try to make the scorelines more responsible.
Leeds Manager, Jesse March, decided to rest all his three goal scorers, Rodrigo Harrison and Aaronson, with Gelhardt, Greenwood and Klich in a triple change.
As if things were not bad enough, Koulibaly piled more misery for his Chelsea side when he got sent off in the 84th minute for a second bookable offence after pulling back Gelhardt who was pacing towards goal.
By now, we all knew who the winner was and Tuchel decided to patch things up at the back by taken off new signing, Raheem Sterling and putting in Azpilicueta in the 87th minute.
Leeds saw out the match and prevailed in a 3-0 home win that sent shockwaves across all England.
In all honesty, Jesse March and his charges did their homework and thoroughly deserved the victory despite being the underdogs.