Chalmers, who stunned the swimming world when he stormed home to win gold in the 100m freestyle at the 2016 Rio Olympic Games, recorded a time of 48.16 seconds to claim the national championship and qualify for the 2018 Commonwealth Games on the Gold Coast, reports Xinhua news agency.
Chalmers' performance was not without drama after he was the slowest qualifier for the final at 49.17 seconds.
"Again, it proves to me that if I do get in lane one, I can win from outside. It was hard for me tonight because I breathe from the right, so on the way home I couldn't see where anyone else was," Chalmers said following the race on Thursday night.
Jack Cartwright, who sensationally dead-heated with Chalmers in qualifying, remarkably finished second in the final.
Defending champion and fastest qualifier Cameron McEvoy finished third, enough to qualify for a place in the 100m field at the Commonwealth Games, while two-time world champion James Magnussen could only manage fourth spot meaning he will only compete in the relay at the games.
Earlier on Thursday night, 17-year-old Tasmanian Ariarne Titmus broke the Australian record for the women's 400m freestyle for the second time in her short career, swimming a time of 4:02.36, more than five seconds faster than second place.
In the men's 400m freestyle, Olympic champion Mack Horton won the Australian championship in a time of 3:45.41, almost four seconds slower than the time that won him the gold medal in 2016, saying he had to "fight a bit harder" for the win than he expected.
Having qualified for the 200m freestyle relay at the Commonwealth Games on Wednesday night, Horton said that he was "on the pain train" following the 400m.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
