On a night young back-rower Jermaine McEwen made everyone sit up and take notice with a two-try display at Allianz Stadium, the undermanned Knights advanced to next week's semi-final by upstaging Souths on their home patch.
The Knights will face the loser of Saturday's qualification between the Warriors and the Dolphins, after claiming their first finals win on the road since 2013.
Without five-eighth Dylan Brown and their first-choice front-row pairing of Trey Mooney and Daniel Saifiti, there would have been few pundits who would have given Newcastle a chance before kick-off on Friday.
But, inspired by Dane Gagai's running battle with South Sydney's Latrell Mitchell, last year's wooden spooners kept their premiership ambitions alive in front of a 28,152 crowd that included a healthy contingent of Novocastrians.
"I think the belief and confidence that coach (Justin Holbrook) instills in us, we don't worry about what we don't have," said Newcastle captain Kalyn Ponga.
"To have them (Newcastle fans) here impacting our performance is pretty special ... obviously we made them proud tonight and have all year but we have a few more to go."
On the other hand, next to nothing went right for the Bunnies in their first finals game since 2023.
Alex Johnston (groin) and Cody Walker (calf) trudged off with injuries, while Mitchell was largely kept quiet by Gagai who formed part of a fruitful right edge that was the Knights' main source of attack.
McEwen drew first blood down that side when he caught a Dom Young bat-back and raced in from 30m out to score a sixth minute opener.
Mitchell and Gagai's skirmish boiled over soon afterwards but when neither player landed a clean blow, referee Ashley Klein allowed both to stay on the field.
"It was a great battle and was always going to be so, but Gags was tremendous for us and did a really good job," Holbrook said.
The fracas injected some venom into a game in which the Knights slowly began to take the upper hand.
McEwen and fellow edge Francis Manuleleua made their presence felt on the Bunnies' edges before Gagai raced past Mitchell to dot down on a Sandon Smith grubber.
Rabbitohs winger Campbell Graham crashed over Greg Marzhew to get his side on the board as they trailed 10-6 at the break.
Souths struggled to connect after Walker limped off late in the second half and their only moment of magic came when Mitchell set the wheels in motion for a Jayden Sullivan try.
The Sullivan try was chalked off after a lengthy bunker review during which Johnston was adjudged to have knocked on.
"I'm over the decisions they make and the impact it has on teams," Souths coach Wayne Bennett said.
"I'd rather have the referee if he is doing his job properly, best he can. He'll make a mistake and I can live with that.
"What I can't live with is this thing called the bunker that's supposed to be 100 per cent perfect. It's not perfect."
Young helped swing the result in Newcastle's favour by making a break down the right to set up McEwen for his second try in the 62nd minute.
Four minutes later, the big English winger tip-toed down the sideline to score and all but send Holbrook's men into week two of the finals.
Jye Gray scored a late try but the Bunnies had left their run too late.
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