Ethical veganism is a "philosophical belief" and so is protected in law, a tribunal has ruled for the first time.
The landmark legal case was brought by vegan Jordi Casamitjana, who claims he was sacked by the League Against Cruel Sports because of his ethical veganism.
His former employer says he was dismissed for gross misconduct.
The judge ruled that ethical vegans should be entitled to similar legal protections in British workplaces as those who hold religious beliefs.
He is yet to rule on Mr Casamitjana's dismissal - which is due at a later date.
Mr Casamitjana, 55, who lives in London, said he was "extremely happy" with the ruling - which is ongoing - adding that he hopes fellow vegans "will benefit".
The tribunal centres on his claim that he was sacked by the animal welfare charity League Against Cruel Sports after disclosing it invested pension funds in firms involved in animal testing.
Mr Casamitjana says when he drew his bosses' attention to the pension fund investments, they did nothing so he informed colleagues and was sacked as a result.
The League Against Cruel Sports says it is "factually wrong" to link Mr Casamitjana's dismissal to his veganism. The charity did not contest that ethical veganism should be protected.
A vegan is someone who does not eat or use animal products.
Some people choose to simply follow a vegan diet - that is, a plant-based diet avoiding all animal products such as dairy, eggs, honey, meat and fish.
But ethical vegans try to exclude all forms of animal exploitation from their lifestyle. For instance, they avoid wearing or buying clothing made from wool or leather, or toiletries from companies that carry out animal testing.
"Religion or belief" is one of nine "protected characteristics" covered by the Equality Act 2010.
The judge Robin Postle ruled that ethical veganism qualifies as a philosophical belief under the Equality Act 2010 by satisfying several tests - including that it is worthy of respect in a democratic society, not incompatible with human dignity and not conflicting with the fundamental rights of others.
At the tribunal in Norwich on Friday, the judge said in his ruling that ethical veganism was "important" and "worthy" of respect in a democratic society.
He said: "I am satisfied overwhelmingly that ethical veganism does constitute a philosophical belief."