Australia’s Cameron McEvoy has won the men’s 50m freestyle gold medal at the Olympics.

McEvoy collects Australia’s ninth gold medal at the Paris Games with his victory at the La Defense Arena on Friday night.

The 30-year-old, the first Australian man to swim at four Olympics, triumphed in 21.25 seconds in the one-lap dash.

The win is McEvoy’s first Olympic gold and helps erase his lingering disappointment from the Rio Games eight years ago.

In Brazil, McEvoy was hot favourite for the 100m freestyle but finished seventh in a final won by compatriot Kyle Chalmers.

McEvoy took an extended break from the swimming after the Tokyo Olympics three years ago when disillusioned with the sport.

But he returned to the pool with a self-styled revolutionary training regime.

A physics student nicknamed The Professor who aspires to be an astronaut, McEvoy bases his training around technical minutia in the water.

But outside the pool, he retains fitness with activities such as calisthenics and rock climbing rather than swimming endless laps.

McEvoy delivers Australia’s swim team a sixth gold medal in Paris.

He joins Ariarne Titmus (women’s 400m freestyle), the women’s 4x100m freestyle relay team, Mollie O’Callaghan (women’s 200m freestyle), Kaylee McKeown (women’s 100m backstroke) and the women’s 4x200m freestyle team as winners in the French capital.