British actress and AIDS campaigner Richardson died in March after suffering brain trauma following a skiing accident in Montreal.
Basic Instinct star Stone was a close friend of Irish actor Liam Neeson's wife, and she made sure to honor the tragic star as she took to the stage for the annual Cinema Against AIDS fundraiser in the South of France, held by nonprofit organization amfAR.
An emotional Stone told the audience, "This year we lost an angel from our amfAR family. It was one of those random events that leaves you in a state of shock and profound grief. In March, the funny, graceful Natasha Richardson was taken from us.
"People say, 'Oh, she can't really have been that great or graceful.' She was. 'That funny, charming, sweet and elegant.' She was. She left behind her husband and two stunningly beautiful children and an unfinished mission to help us find a cure for AIDS."
Richardson's support for AIDS charity amfAR has been continued by her husband Neeson, who sent a note for Stone to read out at the event, urging everyone to keep up their tireless campaigning.
Stone pledged $50,000 in honor of Richardson, before Annie Lennox took to the stage to perform "Talking to An Angel," which she dedicated to the late star's memory, saying, "That was for Natasha."
Richardson leaves behind her two sons with Neeson -- Michael, 13, and Daniel, 12.
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