NANTERRE, France — Ariarne Titmus knocked off Katie Ledecky again at the Olympics, winning the 400-meter freestyle Saturday in one of the most highly anticipated races of the Paris Games.

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

With her fingernails painted Aussie yellow, Titmus led from start to finish. She faced her stiffest challenge from Canadian phenom Summer McIntosh but won comfortably in 3 minutes, 57.49 seconds.

McIntosh claimed the silver in 3:58.37. Ledecky was left in their wake and got the bronze in 4:00.86.

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

Titmus 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.

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.

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.