Ellie Salthouse's quest for an elusive world triathlon championships podium has taken a step forward, with another win at the Ironman Melbourne 70.3 race.

Jarrod Osborne had the biggest win of his career in the men's race on Sunday at suburban St Kilda, beating Olympian Jake Birtwhistle.

Salthouse, who also won the Melbourne 70.3 race two years ago, is preparing for the Ironman 70.3 worlds on December 14-15 in Taupo, New Zealand.

"I would love a podium, my best result at a world championship is eighth, so I'm definitely looking to better that - I know I can," said the Queenslander, who has a solid resume of long-course results.

Salthouse won the 1.9km swim, 90km cycle and 21.1km run event in four hours three minutes 29 seconds.

She duelled for most of the run with Swede Anna Bergsten, dropping her with less than three kilometres left.

Bergsten finished 31 seconds later and Australian Radka Kahlefeldt was third in 4:06:31.

"It wasn't quite the fast day that I wanted ... but I'm always stoked with the win and I had a surprisingly great run - I wasn't expecting to have some good run legs today," Salthouse said.

"I've never run side-by-side with anyone for 19km, in my whole life, so that was thrilling and a little bit frustrating at times.

"But I managed to drop Anna with about 2.5km to go ... the rubber band just snapped and I thought 'thank God'."

South African Jamie Riddle, who raced at the Paris Olympics, led until midway through the men's run, when he pulled out because of a leg injury.

Osborne then dropped Birtwhistle with about 5km left and the Canberra triathlete revelled in the perfect conditions, winning in a course-record 3:35:21.

Birtwhistle finished one minute 45 seconds back and Nick Free made it an all-Australian podium.

"It's pretty amazing, I wasn't expecting that at all. It's just one of those days where everything comes together and it feels good," Osborne said.

Osborne played AFL - he was in the Sydney reserves - before switching sports because of the COVID-19 disruptions.

He is preparing for the Asia-Pacific Ironman 70.3 championships on December 1 in Busselton, south of Perth.