Protest rallies are planned in more than a dozen Australian towns and cities over plans to close remote Aboriginal communities.
Adelaide rally co-organiser Tanya Hunter said there was also international support, which made it a significant event.
"It is overwhelming; we've got over 85 actions worldwide and nationally taking part," Ms Hunter said.
"And it's just comforting as well to know that people around the world are actually beginning to become aware of Aboriginal issues in this country, and the support has come at a critical time."
The Western Australian (WA) Government says a one-off $90 million payment by the Federal Government to look after the remote settlements is unsustainable. Protests against its plans to close the communities have been organised by Aboriginal rights movement SOS Black Australia.
Ms Hunter said she could not get over how enormous the support for Aboriginal people was.
"I think it'll be fair to say [that this event is the biggest Aboriginal rights demonstration in Australia]; it's quite an historical moment.
"I haven't seen anything like it in a long time, and I think the rest of Australia and the Aboriginal community feel the same way."
She said that even a lot of white Australians were in an uproar about the WA Government's decision.
Ms Hunter belongs to the Ngarluma mob (an Aboriginal term for large tribal grouping) from the Pilbara region and the Nyikina mob from the Kimberley region, both of which are in Western Australia.
She said that although the WA Government was making a bad decision, it was in a way doing Aboriginal people a favour by exposing to the world how it treated indigenous communities.
Wider support
A Māori rights movement based in South Australia, 'Iwi n Aus', is supporting the marches. Many New Zealanders based across the Tasman have also been vocal in their opposition to the WA Government's plans.
Ms Hunter said it was comforting to know that Māori brothers and sisters were behind the movement.
Marches have been called in in six New Zealand centres: Auckland, Hamilton, Tauranga, Wellington, Christchurch and Dunedin.
Internationally, protests are planned in Los Angeles, Chicago, Denver, Honolulu, Houston, New York, Ottawa, Toronto, Hong Kong, Berlin and London.