Israel Folau has launched legal proceedings with the Fair Work Commission against Rugby Australia and the Waratahs.
Folau's lawyers said it was unlawful to terminate employment on the basis of religion under Section 772 of the Fair Work Act.
In a statement, Folau said: "No Australian of any faith should be fired for practising their religion." Folau is seeking substantial remedies according to his lawyers.
Folau had his $4 million contract with the RA terminated following a series of social media posts, including an Instagram post in April that condemned drunks, homosexuals, adulterers, liars, fornicators, thieves, atheists and idolaters to hell.
The 30-year-old, who has refused to remove the offensive posts, had his contract torn up after being found guilty of a high-level breach of the organisation's code of conduct.