Ariarne Titmus was defeated at the finish by her American rival in the 400m freestyle series

Australian favourite Ariarne Titmus was defeated by American Katie Ledecky in a thrilling run in the 400m freestyle on the opening day of the Olympic Games.

Titmus, who won the event at the Tokyo Olympics, seemed on her way to victory, but her main rival came from behind and took the honours in the last 50 metres.

Ledecky posted a time of 4:02.19, just ahead of Titmus at 4:02.46. The duo posted the two fastest times in the three heats.

Titmus, the world record holder and five-time gold medalist, will now swim in lane five in Sunday’s final.

“If you just look at Arnie at the end of that race, she didn’t actually look that tired,” Giaan Rooney said on Channel Nine.

‘It didn’t look comfortable in that last 100 meters, but I also wonder if that was a bit of a game of ‘I don’t want to burn everything I have this morning, if you want to do that time then do it, I don’t have to do that’.

The rivalry between Ledecky and Titmus heated up a notch this week, when the American cleverly outplayed her rival ahead of their battle for Olympic gold.

Ledecky, the most successful swimmer ever with seven Olympic gold medals and 21 world championship gold medals, refused to mention Titmus’ name during a crowded press event in Paris.

Katie Ledecky of the United States (left) and Ariarne Titmus of Australia (right) react after a 400m freestyle heat at the Paris 2024 Olympic Games

Australia’s Ariarne Titmus is seen during a heat of the women’s 400m freestyle at the 2024 Olympic Games.

Until Saturday, the American superstar had not beaten the Australian superstar in the 400m freestyle for five years, and was unable to thank Titmus in person.

“I think I’ll get a chance, but yeah, that’s who I am and I feel like I’m ready to race. That’s all you can ask for,” Ledecky said.

‘So I’m going to give it my best shot and it’s obviously a great field, top to bottom. A lot of people who have a chance, so I’m just going to put in a great race in the morning and in the evening and see where I end up.

“They are amazing athletes and I’ve had the chance to compete against them quite a few times over the years, especially Summer (McIntosh) who trained in the US and has competed a lot over the last few years.

Ledecky and Ariarne Titmus (pictured) battle for Olympic gold in the 400-meter freestyle in one of the most anticipated showdowns of the Games

“It’s always fun to race against the best and we had the three best times ever in that race. It makes for a great field and a great race.”

“Those two have continued to improve the game, improve my game. I know I have to give my best. I think they know they have to give their best.”

Another Australian also made it to the final: Jamie Perkins qualified fifth.

New Zealand’s Erika Fairweather (third fastest qualifier) ​​and Canada’s McIntosh (fourth fastest) both swam well, promising an exciting final tomorrow.