NANTERRE, France >> It was billed as one of the most anticipated races of the Paris Olympics.

Ariarne Titmus turned it into a blowout.

Titmus left Katie Ledecky in her wake at La Defense Arena, leading from start to finish to win the 400-meter freestyle Saturday night.

Titmus, the Australian star known as “Terminator,” handed Ledecky a second straight Olympic defeat in an event the American won at Rio de Janeiro in 2016.

With her fingernails painted Aussie yellow, Titmus strolled on deck with the confidence of a reigning champion, flashing a big smile and waving to the fans.

Titmus knew she was the swimmer to the beat, even with one of the greatest ever in the lane next to her.

Then, she went out and proved it.

Titmus actually faced her stiffest challenge from Canadian 17-year-old phenom Summer McIntosh but won comfortably in 3 minutes, 57.49 seconds.

McIntosh claimed the silver in 3:58.37. Ledecky wasn’t even close, settling for bronze in 4:00.86.

“My legs are a bit tired, but I’m just relieved more than anything,” Titmus said. “I probably felt the expectation and pressure for this race more than anything in my life, to be honest, and I’m pretty good at handling the pressure of it.”

Ledecky, 27, remains at six individual gold medals in her brilliant career, still the most of any female swimmer in Olympic history.

“It’s always good to get a medal for Team USA,” Ledecky said. “I want to be a little faster, but I can’t complain with the medal.”

Titmus. 23, now has three individual Olympic victories on her growing resume. She swept the 200 and 400 free in Tokyo and is favored to pull off the same double in Paris.

“I’m just happy to get the result for myself and I feel so honored to be a part of the race and be alongside legends like Katie,” Titmus said. “I look up to her so much as an athlete and it’s certainly not a rivalry beyond the races. I really respect her as a person.”

Ledecky isn’t done yet. She skipped a chance to face Titmus again in the 200 free, but the American is favored to take gold in both the 800 and 1,500.

She shrugged off any talk of a rivalry.

“It’s a friendship, if anything,” Ledecky said. “We have a lot of respect for each other and we love competing against each other. It brings the best out of each of us and I’m sure, you know, pushes each of us in training knowing that we have each other to race at these kinds of meets.”

Australia made it 2-for-2 against the rivals from the U.S. in the women’s 4x100 freestyle relay, claiming their fourth straight Olympic title in that event.

The quartet of Mollie O’Callaghan, Shayna Jack, Emma McKeon and Meg Harris set an Olympic record with a winning time of 3:28.92.

The Americans — Kate Douglass, Gretchen Walsh, Torri Huske and Simone Manuel — rallied to take silver in 3:30.20. They edged China’s team of Yang Junxuan, Cheng Yujie, Zhang Yufei and Wu Qingfeng by a tenth of a second.

The U.S. capped the night with another gold medal for Caeleb Dressel, who anchored a dominating victory in the men’s 4x100 freestyle relay.

It was the eighth medal of Dressel’s career — all of them gold.

The two youngsters who beat Dressel at the U.S. trials in the 100 freestyle, Jack Alexy and Chris Guiliano, started things off for the Americans. Then it was Hunter Armstrong turning the fastest leg of all to give Dressel a commanding lead to work with at the end.

He won going away in 3:09.28, pumping his fist and slapping hands with his teammates when he saw another No. 1 beside their names.

Australia, anchored by Kyle Chalmers, took the silver in 3:10.35, while the bronze went to Italy in 3:10.70.

Germany’s Lukas Märtens won the first swimming gold of these Games, knocking off three world champions in the men’s 400 freestyle.

Märtens set a blistering pace through the first 300 meters and held on at the end to touch in 3:41.78. The silver went to Elijah Winnington of Australia, the 2022 world champ, in 3:42.21. Reigning world champion Kim Woo-win of South Korea settled for bronze in 3:42.50.

Ledecky posted the fastest qualifying time in the morning heats, but Titmus was clearly saving herself for the race that mattered most.

She went nearly 5 seconds faster in the evening, while Ledecky shaved less than 1 1/2 seconds off her morning time.

“We knew it was going to be a great race going in,” Ledecky said. “So many, great swimmers in that field. I knew it would be tough and everyone in that field put up a great race and swam really, really well,”

It was a strong opening to the Games for the 17-year-old McIntosh, who claimed the first of what could be multiple medals in Paris. She’s the world-record holder in the 400 individual medley.

“I hope that we put on a good show tonight,” Titmus said, “and everyone enjoyed it.”

No complaints from the Terminator, that’s for sure.