The BHP Foundation will donate A$2 million (US$1.4 million) to the Australian Red Cross to support emergency relief efforts to bushfire impacted regions around Australia.
The company described the loss of lives and livelihoods from the bushfires as tragic and devastating.
Meanwhile, Rio has donated a further $750,000 to the Red Cross' disaster relief and recovery efforts, adding to the $250,000 it donated in November.
Rio is also providing employees involved in current volunteer firefighting efforts with full leave entitlements.
"With the escalation in the bushfire crisis, which has caused devastation for many Australians, we have increased our donation to $1 million to support the Red Cross in its tireless work caring for affected communities," Rio CEO Jean-Sebastien Jacques said.
"We are also ensuring any of our employees involved in firefighting and relief efforts are supported throughout this period with full leave entitlements.
"Beyond these steps announced today, we will continue to explore ways to help impacted communities in this time of need."
South32 donated $500,000 to the NSW Rural Fire Service and Rural Fire Brigades Association Queensland in November, and pledged to match employee contributions.