The Giants had clawed back a game-high 42-point deficit in the third quarter to level the scores at 13.7 (85) early in the fourth at Engie Stadium on Saturday.
But after the Hawks steadied, Sam Butler kicked truly to give them a seven-point lead 17 minutes into the last term, before Mabior Chol slotted two straight goals for the cherry on top in a 16.11 (107) to 13.10 (88) win.
Hawthorn set up a semi-final with minor premiers Adelaide, while it's season over for GWS.
Jai Newcombe was electric in the midfield with 31 touches and 11 clearances, while Jarman Impey starred in defence with 28 disposals.
A suspected ACL tear to Giants youngster Darcy Jones added to the Giants' woes.
Talented small forward Jones's right knee buckled after he landed awkwardly following an attempted tackle on Massimo D'Ambrosio.
The 21-year-old, who was in tears and consoled by coach Adam Kingsley on the sidelines, was able to walk without support on his way to the rooms.
He had a goal from five touches to his name before he was replaced by Josh Kelly, on return from a calf injury.
Super substitute Kelly then inspired the third-quarter fightback, gathering 18 touches and kicking two goals.
With 28 points the difference at halftime, comeback specialists GWS slammed through six straight majors in 15 minutes to reduce the deficit to six points before Jesse Hogan squared the ledger with his third goal.
Hawthorn made GWS pay for their ill-discipline to build a 24-point lead in the first quarter.
Newcombe, in his 100th game, kicked the Hawks machine into gear with the opener after being gifted an extra 50 metres by Jones, who had encroached on the mark.
Karl Amon then slotted Hawthorn's fourth straight goal after opposition forward Callum Brown gave up grass for rough conduct against James Worpel.
GWS finally hit the scoreboard when Dylan Moore mistakenly handpassed to opponent Ryan Angwin, who then set up Finn Callaghan's major.
The home side had pulled off 12 to one inside-50 entries before Newcombe's goal, but had only two behinds to show for it.
GWS got momentum back on their side after the first break thanks to a soccer goal from Kieren Briggs and another from Hogan, on return from a foot injury.
But Hawthorn were able to rise to the challenge, with Jack Gunston kicking two straight goals to make it three before halftime.
Flashy Hawks forward Jack Ginnivan also slammed through two goals in the third quarter, and celebrated accordingly, before GWS came roaring back with seven unanswered goals.
16°C