Australian rugby international Israel Folau is seeking "substantial remedies" after being sacked for a social media post saying "hell awaits" gay people.
The 30-year-old devout Christian had his contract terminated by Rugby Australia and has now launched legal action against RA.
Folau is claiming his employment was unlawfully terminated.
"No Australian of any faith should be fired for practising their religion," Folau said.
A case has been filed with Australia's Fair Workplace Commission, an industrial relations tribunal.
"Ours is an amazing country built on important principles, including freedom of religion. A nation made up of so many different faiths and cultural backgrounds will never be truly rich unless this freedom applies to all of us," Folau, who played club rugby for New South Wales Waratahs, added.
"The messages of support we have received over these difficult few weeks have made me realise there are many Australians who feel their fundamental rights are being steadily eroded."
The application says: "Accordingly, Mr Folau is seeking substantial remedies from his former employers should they be found to have breached the Fair Work Act in terminating his employment."
The full-back, who has played 73 Tests for Australia and was expected to represent his national side at this year's Rugby World Cup, had a contract until 2022.
As well as the termination of his contract, he lost sponsorship deals with companies including car manufacturer Land Rover and sportswear brand Asics.
He could be seeking up to AUS$10m (£5.5m) in damages, according to the Sydney Morning Herald.
Rugby Australia and New South Wales Rugby later issued a joint statement which stressed Folau had been sacked "because of a serious breach of the Professional Players Code of Conduct".
"This is an issue of an employee and his obligations to his employers within the contract that he signed," the statement added.
"He was bound by a Code of Conduct for all professional players in Australia that spells out clear guidelines and obligations regarding player behaviour, including respectful use of social media."
Brother released for personal reasons
Folau's younger brother John was also under contract with the Waratahs and the 24-year-old back, who was yet to make his Super Rugby debut after being signed before the 2019 season, has been granted an immediate release for personal reasons.
"We gave John some time off for leave and he has come back to us recently and asked for a release, which we're happy to grant," said Waratahs coach Daryl Gibson.
"John has been in a difficult position for the last wee while. He has got really divided loyalties to his family and his brother and then also to the team. He wanted to stress how much he enjoyed being with the team and what a difficult decision it was for him."
Source: BBC Rugby Union News