Dane Daniel Bakegaard and Fella Langridge of Great Britain have posted the fastest times in Australia for an Ironman-distance triathlon with scorching debuts at Busselton.

The two internationals dominated Sunday's Ironman WA event south of Perth, with Bakegaard breaking the course record by nearly 11 minutes.

Langridge went under the women's mark, also set in 2019, by nine minutes.

The 3.8km swim, 180km cycle and 42.2km run course at Busselton is noted for fast times and competitors on Sunday made the most of ideal wind conditions.

Bakegaard won in seven hours 34 minutes 23 seconds, six minutes ahead of Perth's Matt Burton, who also set the fastest time by an Australian.

Nick Thompson, also from WA, rounded out the podium, eight minutes after Burton.

"I'm feeling pretty terrible to be honest - it's Ironman, it's not supposed to feel good," Baakegard said at the finish.

"Seriously though, the crowds here, the whole course and everything, it was just spectacular to race.

"It's definitely a bucket list race to do and in some weird way I actually appreciated every second of it."

Langridge finished in 8:29:43, beating Lisa Norden from Sweden by three minutes, with Dutch triathlete Lotte Wilms third.

Els Visser, also from The Netherlands, was fourth and Chloe Lane was the first Australian woman in fifth place.

Langridge passed Norden during the marathon run to claim her first Ironman-distance win.

"They're harder to get these days with fields getting even more competitive so it's nothing to take for granted and I'll remember it for the rest of my life, it was amazing," she said of her win.

Ironman WA and the Ironman 70.3 (half-Ironman) races at Busselton on Sunday attracted more than 3000 entrants.

Former Essendon AFL player David Zaharakis made an impressive Ironman debut, clocking 10:19:31 in the 30-34 age group category.