In front of 59,725 fans at Optus Stadium on Friday night, Fremantle skipped out to a 38-7 lead before Geelong hit the front in the third quarter on the back of three quick goals to Oliver Henry.
Staring down the barrel of a straight-sets finals exit, Fremantle lifted when it mattered most, with Jackson the biggest hero of them all.
The man affectionately nicknamed "the Unicorn" kicked two late goals in the third quarter and set up another for Patrick Voss to give Fremantle back the lead.
In a pressure-filled final term, Geelong cut a 24-point deficit back to eight points with 75 seconds remaining.
But Wharfie Time - played for just the second time this year - sent the crowd into a frenzy, with Voss kicking his fourth goal from the ensuing centre clearance as Fremantle sealed the 18.12 (120) to 16.10 (106) victory.
The win set up a preliminary final against the Swans in Sydney next week.
Not only will Sydney be without suspended quintet Isaac Heeney, Chad Warner, Nick Blakey, James Jordon and Riley Bice, but captain Callum Mills is also missing after suffering a season-ending knee injury in last week's win over Brisbane.
Henry kicked a career-high five goals for Geelong, while Shannon Neale chipped in with three.
Geelong had made eight preliminary finals in the past 10 seasons, but having to travel to Perth for this year's semi-final proved a bridge too far.
Bailey Smith racked up 29 disposals and 751m gained, while Patrick Dangerfield followed up his five-goal haul against Carlton with two majors and two goal assists.
Jackson (25 disposals, 35 hitouts, eight clearances, two goals) was a clear best-on-ground, while Voss's four goals were also crucial.
Shai Bolton made up for his quiet display in last week's 32-point loss to Hawthorn with two goals from 26 disposals.
Fremantle had kicked a total of just two first-quarter goals in their previous four finals under coach Justin Longmuir.
But they blew that to bits with six goals in the opening term against the Cats, with their run-and-gun mindset proving irresistable.
Bolton got the party started with two goals in the opening two minutes, including a dodging and weaving effort from 52m out.
Voss got in on the act with two goals of his own.
And by the time Mason Cox kicked truly after taking an uncontested mark 20m out from goal, Fremantle led 38-7 and Optus Stadium was rocking.
The Dockers won the inside-50m count 20-12 in the second quarter, but Dangerfield's strength ensured Geelong won the term five goals to four.
Dangerfield played a role in three of those goals, including one instance when he scrapped on the turf with Dockers players all around him before firing off a handball for Shaun Mannagh to score.
Another Dangerfield handball set up Jeremy Cameron for his first goal since round 15.
In a topsy-turvy third quarter, Geelong dominated the midfield battle for most of the term to kick 5.6, including three majors to Henry.
But the Cats' eight-point lead vanished in the blink of an eye as Jackson went into overdrive for the final five minutes of the term.
Jackson kicked two goals - and it would have been three had his spectacular volley not been rubbed out due to Michael Frederick going over the boundary line in the lead-up.
The late flurry from Jackson - including a goal after the siren - gave Fremantle a 16-point edge heading into the final quarter, and Fremantle held their nerve to secure the win.
10°C