Ariarne Titmus' coach has launched into a celebration for the ages after his 20-year-old charge claimed gold in a titanic 400m freestyle final.

Titmus had Aussies on the edge of their seats around the world after holding off rival Katie Ledecky to claim the win in a time of 3:56.69.

After taking in the young star’s reaction from the pool, the cameras cut to Dean Boxall in the stands as he jumped into a monster fist pump before taking hold of some safety barriers and giving them a big shake.

“Dean Boxall = ALL OF US RIGHT NOW,” Aussie model Erin Holland tweeted, as the incredible vision instantly began circulating on social media.

Entertainment Tonight editor Stacy Lambe chimed in: “There’s reacting to the Olympics, and then there’s Dean Boxall.”

Another — Triple M’s Rudi Edsall — said Boxall had captured “the mood of the nation”.

On the telecast swimming great Ian Thorpe described Boxall as the “contemporary version of Laurie Lawrence”, a reference to the legendary Australian coach’s famous celebration of Duncan Armstrong’s 200m freestyle gold in Seoul in 1988.

At one point an Olympics official attempts to contain Boxall to his zone. However she seemed a little puzzled about just how to do so, with very little likely to temper the Australian’s euphoric moment.

“Good luck to the IOC/Games Official whose job it will be to try to lecture Dean Boxall re mask wearing.. and staying in his allocated spectator zone,” journalist Heidi Murphy posted.

NBC’s Matt Brickman shared: “Just want to watch a video of Australia swim coach Dean Boxall losing his mind, while a somewhat terrified #Olympics staffer tries to calm/redirect him, on a loop forever.”

Titmus was told about the celebration after her incredible victory.

“He means everything to me. Coming into this race we knew what we had to do,” she said.

“We didn’t discuss what I wanted to do in the pool. It was more of a have fun moment. I love you. Have fun. We practised this for so long. I just knew what I had to do when I got out there.”

Titmus triumphed in a historic final on Monday, defeating the United States' five-time Olympic champion Ledecky.

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Titmus' achievement is Australia's second gold medal of the Tokyo Games, following the women's 4x100m freestyle relay success.

And it delivers Ledecky, regarded as the greatest female swimmer ever, her first defeat in an Olympic final.