In front of a sellout 55,966 crowd on Thursday night, Fremantle entered the half-time break with 0.11 to their name - marking just the third time in the club's 32-year history they had been goalless in the first half.
Sydney led 33-11 at the main break - after leading by as much as 25 points in the second quarter - but the Dockers unleashed a blistering 15-goal second half to secure the 15.21 (111) to 10.13 (73) win.
The result put Fremantle (15-2) two wins clear of Sydney (13-4) on top of the table, and got the Dockers back on the winners' list after their 14-game victory run was ended by GWS last week.
Josh Treacy kicked 4.4 for Fremantle in a huge effort in attack, while Shai Bolton (two goals, 23 disposals), Caleb Serong (28 disposals) and Murphy Reid (28 disposals) were creative.
But it was Fremantle captain Alex Pearce who evoked the biggest cheers from the crowd after pulling off a series of clutch goal-saving marks and intercepts.
Sydney spearhead Charlie Curnow kicked five goals to snatch the Coleman Medal lead, while Errol Gulden starred with 30 disposals.
But the way Fremantle destroyed their fellow flag fancies in the second half - scoring 100 points across the final two quarters - is set to send shivers through the rest of the competition.
Sydney laid 40 tackles to 21 in the first half to put the home side under immense pressure.
Tom Papley kicked the opening goal of the match and was a menace for the rest of the first term, but Fremantle were their own worst enemies at times with poor disposal execution.
Their biggest gaffe came when Chad Warner missed a set-shot snap on goal.
Dockers defender Luke Ryan, who had given up the initial free kick after being caught holding the ball, ran up to Warner and condescendingly rubbed his opponent's hair after the missed snap.
The incident led to Curnow being handed a free kick at the top of the goal square.
Sydney entered the first break with a 24-5 edge, and there was just one goal in the second quarter - to Papley - as Fremantle's stars flailed in front of the big sticks.
It took a defender to finally break Fremantle's goal drought, with Jordan Clark kicking truly on the run from beyond 50m to get the Dockers' first major just 49 seconds into the third quarter.
In what became a goalfest of a quarter, Curnow kicked three goals - including two long-range beauties from near the boundary - to keep Sydney's noses in front.
But Fremantle's six-goal quarter meant they entered the final change with just a two-point deficit and all the momentum.
Dane Rampe gave up a silly free kick in the third quarter for rubbing the hair of Jye Amiss.
The Fremantle spearhead missed that set shot, but Rampe gave him another chance early in the final quarter when he held Amiss off the ball.
This time around Amiss nailed the goal, giving Fremantle the lead for the first time in the match.
Curnow kicked his fifth to give Sydney back the advantage, but Fremantle slammed through the next seven goals to put the Swans to the sword.
FREMANTLE'S PREVIOUS GOALLESS FIRST HALVES
* Round 15, 2009 - Fremantle scored 0.1 (1) in the first half on the way to a 19.16 (130) to 1.7 (13) loss to Adelaide at Football Park
* Round 8, 2020 - Fremantle scored 0.3 (3) in the first half on the way to a 6.12 (48) to 2.4 (16) loss to Geelong at Optus Stadium
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