According to sources, the 'Baby' singer pledged an incredible $545,000 while attending the glitzy amfAR Cinema Against Aids event at the Cannes Film Festival last week.
Although Justin, 20, hasn't directly said anything about the reports, US websites including TMZ and InTouch Weekly both claim he made the gesture after a fellow guest pledged $545,000 and he decided to match it, saying he wanted to do something good.
The only reference Justin has made to the amfAR event online is one simple tweet: "Amfar #giveback." The money raised from the event will go AIDS research.
He also retweeted the organisation's official account, which said: "A new generation is ready to stand up and support. Thank you for joining us tonight, @justinbieber. #amfARCannes."
Although the Biebs has been in the headlines for less positive things lately (that Miami incident, egg throwing etc.), he does actually support a slew of charitable organisations, including Pencils of Promise, which he frequently references on social media.
The non-profit organisation - founded by Justin's manager Scooter Braun's brother Adam - builds schools and increases opportunities for education in the developing world.
Justin is currently in Monaco, where he was seen sunbathing shirtless on a yacht yesterday and enjoying the Monaco Grand Prix.
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