Knight, who lived in Beaufort, near Ballarat in regional Victoria, was attending the Rock&Cars festival in southern France.
According to French media reports, the 54-year-old was standing under a tree with five other people when a branch struck him, leaving him with fatal injuries.
Knight was well known for his comedy show, Mad Dogs and an Englishman, which he performed in Australian venues and overseas.
He also ran dog behavioural classes.
Knight’s partner of 15 years, Hayley, has flown to France after receiving news of the tragic accident.
Hayley’s sister, Joanne Allen, paid tribute to Knight, saying he was “healthy, happy and had everything going for him”.
“He was charismatic, funny, passionate and so very loved by Hayley, his family and his friends all over the world,” Allen wrote in a GoFundMe page.
Knight had been scheduled to perform his shows in the UK during his overseas trip as well as running his popular dog behavioural classes in Europe.
The comedian usually visited France annually, where he had a home, and was only in the country for a few days before the accident happened, Allen wrote.
“We are beyond devastated that his life was taken by a freak accident …an accident that we are all still trying to comprehend,” Allen wrote.
“Hayley is now living her worst nightmare and facing life without Tony…her soulmate.”