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Social media stars and sporting champions are splashing the cash for Australian bushfire relief efforts and urging fans to do the same.

Twenty-six people have died since the start of the disaster in September, more than 2,000 homes have been destroyed, and some eight million hectares (80,000 square kilometres) has burned -- an area roughly the size of Ireland or South Carolina.

Australian Marvel actor Chris Hemsworth said he would donate AUS$1 million, singers Kylie and Danni Minogue pledged AUS$500,000 to the country's rural firefighters, a donation matched by Nicole Kidman and her husband Keith Urban.

Compatriots including Russell Crowe -- who used his Golden Globe win to speak about the tragedy -- and Rebel Wilson have pledged donations, with singer Dami Im also donating.

Athletes like Lewis Hamilton, tennis players Ashleigh Barty, Maria Sharapova and Novak Djokovic, and cricketers -- including Chris Lynn and Glenn Maxwell -- offered to donate their winnings.

On Wednesday, organisers of the Australian Open said Roger Federer, Williams and Rafael Nadal will headline a charity match ahead of the tournament.

American stars -- including Kylie Jenner, singers Pink, Lizzo, and Shawn Mendes, talkshow host Ellen DeGeneres, and actor Patricia Arquette -- all pledged to contribute to relief efforts.

Leonardo DiCaprio's environmental group, Earth Alliance, also said it was giving US$3 million.