riarne Titmus turned it into a blowout.

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

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.”