Australia's Grace Brown surged home to overhaul compatriot Amanda Spratt at the finish of the third stage and win the women's Tour Down Under on Tuesday in scorching conditions.

Brown, the world time trial silver medallist, reeled in three-time TDU winner Spratt on the seven-kilometre (4.3-mile) descent off the punishing Corkscrew climb to claim the final stage and become the first World Tour winner of the event.

Spratt, who was bidding to add to her 2017-19 TDU wins, held a 20-second gap over Brown after a draining climb up the brutal 24.5 percent gradient of the Corkscrew.

But she couldn't hold off the sprinter Brown in the downhill dash to the finish line outside Adelaide.

"I am really pleased. The team did an awesome job today," Brown said.

"They led me out into the final climb and I knew Amanda was going to be really good on the Corkscrew.

"But I just kept her within distance, knowing that I could potentially catch her on the descent, and was able to do it."

Brown, leading the French FDJ-Suez team, won the general classification by 10 seconds from Spratt (Trek-Segafredo) with New Zealand's Georgia Williams (EF Education-Tibco-SVB) on 19 seconds.

Spratt, fighting back from a condition which narrows the artery and restricts blood flow to the legs, was rated the one to beat in the gruelling final stage because of her hill-climbing reputation.

And Spratt, who trailed Brown by six seconds going into the final day, looked on course to win the stage and take the ochre leader's jersey with her commanding lead at the top of the Corkscrew.

But she succumbed to Brown's superior sprinting qualities.

"We sure are making women's cycling exciting, aren't we?" Spratt said.

"I don't have many regrets. My team rode amazingly well, we had a plan, they positioned me perfectly for the Corkscrew and I attacked it the way I wanted.

"It's never nice when you know that Grace Brown is chasing you on a downhill like that, I was hoping I would get there, but she was too strong at the finish."

Overnight race leader Alexandra Manly (Team Jayco-AlUla) dropped well back on the unforgiving climb and finished 40 seconds behind to lose her chance of making the final race podium.