Chase Kalisz and Jay Litherland win Team USA’s first medals in the pool with a gold and silver in the 400m individual medley.
Kalisz, who trained with the legendary Michael Phelps, led after the halfway stage to win the USA’s first gold medal of the Olympic Games Tokyo 2020 and the first one in the pool.
Kalisz finished in a time of 4:09.42, followed home by his team-mate Litherland, who touched the wall 0.86 seconds behind.
This one-two gave the United States two swimmers on the same Olympic podium for the first time since Beijing 2008.
Australia’s Brendon Smith finished 0.10 adrift of Litherland to claim the bronze.
Kalisz joins Michael Phelps and Ryan Lochte as winners of this Olympic gold. He is hoping to re-establish the United States’ dominance in the event after Japan’s HAGINO Kosuke’s win at Rio 2016 interrupted a run of Olympic gold medals for the Americans that dated back to the 1996 Games in Atlanta.
"It is my lifelong dream. It is what everyone dreams of in the sport," said Kalisz. "I do feel like I let the US down in 2016, even though I swam faster here.
"The US has a proud legacy in the 400m individual medley. This was my redemption story.”
With Hagino opting not to defend the title to concentrate on the 200m individual medley instead, his compatriot SETO Daiya, the current world champion, was the pre-competition favourite.
But things did not go to plan for Seto in the heats and he finished the qualifications in 9th overall, missing out on a place in the final.
Kalisz, who won the silver medal in the event in Rio, became the favourite to claim the gold medal.
New Zealand’s Lewis Clareburt looked to have the better of Kalisz at the halfway point, only for the American to come roaring back, taking the lead going into the final 100 metres.
As Clareburt faded, Litherland and Smith, who swam an Oceanian Record of 4:09.27 in qualification, also made their moves.
But Kalisz held off his rivals to win his first Olympic gold medal and the first of United States’ campaign in Tokyo.
Great Britain’s Max Litchford and David Verraszto of Hungary finished joint fourth in 4:10.59.
Leon Marchand of France was sixth in 4:11.16. New Zealand’s Lewis Clareburt touched in seventh, only 0.06 behind Marchand. Italian Alberto Razzetti finished eighth in 4:11.32.