An inspired performance from Sharks prop Andrew Fifita helped Cronulla overturn a 14-point half-time deficit to stun the Cowboys 18-14 for just their second win at home this season.
A try in the shadows of half-time looked to have sealed the game for the visitors who had performed admirably without star playmaker Johnathan Thurston, but huge second halves from Fifita and James Maloney turned the game on its head with the Sharks running in three unanswered tries to join the Storm at the top of the table on 16 competition points.
Jason Taumalolo was outstanding for the visitors with over 200 metres and a stack of tackle breaks, but even his efforts weren't enough to lift the Cowboys to a crucial win ahead of next week's bye.
A worryingly quiet Maloney burst into life 10 minutes into the second half with the likely Blues five-eighth dummying and stepping his way through the line to cut the Cowboys' lead to eight points.
A monstrous charge by Taumalolo looked to have swung momentum back to the Cowboys but his run was quickly forgotten when Fifita skittled several would-be defenders and then offloaded to a flying Chad Townsend to bring the hosts to within two.
There would be no halting the onslaught as a monster shot by Luke Lewis on Lachlan Coote forced a turnover on halfway, and from the ensuing set Valentine Holmes got on the outside of his man and delivered the right ball to send Sosaia Feki over to hand Cronulla their first lead of the night.
Earlier, Cowboys winger Antonio Winterstein gave his side the lead when he flew through the air to ground the Steeden just inside the left corner post off a Lachlan Coote cut out pass.
Cronulla should have fallen a further two points behind but were let off the hook when Ethan Lowe missed a simple penalty goal from next to the left upright 13 minutes out from half-time.
The Sharks wouldn't be so lucky six minutes later when a beautiful ball from Ray Thompson sent Kyle Feldt streaking away down the right sideline before the Cowboys winger passed back inside to send Ben Hampton for the try.
Southern Cross Group Stadium was then left stunned when a Michael Morgan grubber somehow resulted in a 40/20, with the five-eighth turning provider from the ensuing set to set up Feldt with a pinpoint kick that he did well to ground.
Sharks 18 (James Maloney, Chad Townsend, Sosaia Feki tries; James Maloney 3 goals) def. Cowboys 14 (Antonio Winterstein, Ben Hampton, Kyle Feldt tries; Kyle Feldt 1 goal) at Southern Cross Group Stadium. Half-time: 0-14. Crowd: 8,557.