Gunston kicked five first-half goals as the Hawks opened up a 22-point lead late in the third quarter of Thursday night's thriller at Optus Stadium.
The Hawks still led by 17 points with a little over seven minutes remaining in the fourth as they headed for what looked like a gutsy road win.
But in what is set to send a shudder through the rest of the competition, Fremantle slammed home five goals in quick succession to steal the 12.16 (88) to 11.7 (73) win in front of 54,140 fans.
Josh Treacy kick-started the run with a checkside goal under pressure.
Michael Frederick added two himself - one of which was set up by an inspirational Luke Jackson smother on the wing.
Jye Amiss nailed a snap in between Frederick's two goals after Treacy bustled his way through a tackle to fire off a handball.
And when Hayden Young held his nerve after receiving a free kick, it was game over.
Fremantle's eighth victory on the trot is their biggest winning streak since they won a club-record equalling nine in a row back in 2015.
The Dockers (8-1) will have the chance to match that mark when they face struggling Essendon at the MCG next week.
Hawthorn slipped to a 6-2-1 record, and are set to be without Tom Barrass for the near future after the star backman injured his left hamstring in the second term.
Gunston was unstoppable in the first half on the way to 6.2, but was well held by Brennan Cox after half-time.
Nick Watson kicked three first-half goals before fading.
Caleb Serong was prominent for Fremantle with 28 disposals and eight clearances, while Frederick and Amiss kicked three goals apiece.
Hawthorn big men Lloyd Meek (21 hitouts) and Ned Reeves (18 hitouts) kept Luke Jackson (22 possessions, 22 hitouts, seven clearances) honest until the star Docker exploded in the final quarter.
Gunston took a whopping four marks inside 50m in the opening term for a return of 2.2 opposed to Luke Ryan.
It would have been 3.1, but the ARC correctly picked up that one of Gunston's 'goals' had actually grazed the post.
Fremantle won the clearance battle 10-5 to take a two-point lead into quarter-time, but Watson and Gunston tore the Dockers to shreds in the second term.
Gunston, this time opposed to Brennan Cox, kicked three goals for the quarter while Watson added two as Hawthorn entered the halftime break with a 15-point lead.
It marked the first time in Gunston's 291-game career he had kicked five goals in the first half, and his seven marks inside 50m across the first two quarters represented a major worry for the Dockers.
"I thought Stephen Silvagni probably couldn't have stopped him in the first half the way we were letting them transition the ball," Fremantle coach Justin Longmuir said.
"It's just impossible to stop. So we took that away from them in the second half, which helped Coxy.
"And I thought Cox was a bit more proactive with his positioning, which gave him first look at the ball."
Hawthorn had the game on their terms for most of the third quarter, but their inability to cash in cost them dearly as Fremantle launched an inspirational comeback.
"We know the way we want to play, and we got that at different stages tonight," Hawthorn coach Sam Mitchell said.
"We looked quite potent going inside 50.
"But as the game progressed, the territory became overwhelming, and we couldn't get it into our front half to give us opportunities."
