Chairman Gautam Adani said in Townsville that the board had made its "final investment decision" which marked the "official start" of the Carmichael coal mine -- destined to be one of the world's largest.
The mine has encountered numerous regulatory and legal hurdles, leading to seven years of delays, with a mining lease finally granted last year.
It has also been slammed by environmentalists who say it will hurt the reef, a World Heritage-listed biodiverse site stretching along Australia's northeastern coast, which is already threatened by climate change.
The development proposes exporting coal to India via a massive open-cut and underground coal mine 160 kilometres (100 miles) northwest of Clermont in central Queensland, home to the reef, and a 189-kilometre rail link to port.
The conglomerate forecasts it will produce 60 million tonnes of thermal coal a year for export.
Adani hit out at activists who have challenged the project for years.
"We have been challenged by activists in the courts, in inner city streets, and even outside banks that have not even been approached to finance the project," he said.
"We are still facing activists. But we are committed to this project.
"We are committed to regional Queensland and we are committed to addressing energy poverty in India."
The company said the project would generate 10,000 direct and indirect jobs, with pre-construction works starting in the September quarter of 2017.
Federal Resources Minister Matt Canavan said it had been a long haul to get to this point.
"Can I thank Adani for their commitment to wait, to be here and wait because we have all been waiting for this day," he said.
"Now the time for waiting is over and the time for doing is beginning."
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