Princess Diana's famous "revenge dress" is set to go under the hammer at Sotheby's in December, with a portion of the proceeds benefiting a mental health charity supported by Prince William.

The black, curve-hugging Christina Stambolian gown, worn by Diana in 1994, earned its "revenge dress" moniker due to its plunging neckline, which she wore shortly after infidelity was revealed in her marriage to Prince Charles.

IMAGE4 The iconic black off-the-shoulder "Revenge Dress" worn by Princess Diana, designed by Christina Stambolian, displayed on a mannequin against a gray wall with a red floor.

According to Sotheby's notes for the December 9 auction, a rare copy of the original sales catalogue, numbered and signed by Princess Diana and the dress's designer, will be sold with the gown. This catalogue credits Prince William with originating the idea for the dress's initial sale.

In 1997, shortly before her death, a teenage Prince William encouraged his mother to sell approximately 80 of her garments for cancer and AIDS charities. The "revenge dress" alone sold for about $74,000 at that time, which is approximately $151,000 in today's inflation-adjusted value.

The upcoming auction will see some proceeds directed to the NHS Lothian Charity, acting on behalf of the Royal Edinburgh Hospital, a mental health facility in Scotland. This aligns with the focus of the Royal Foundation of the Prince and Princess of Wales, led by Prince William and Kate Middleton, which champions suicide prevention and destigmatized mental health support.

Fashion and art experts estimate the "revenge dress" could fetch over $1 million, based on the sale of another Jacques Azagury gown previously worn by Princess Diana. Sotheby's offers a more conservative estimate of around $200,000.

Before the auction, the public will have an opportunity to view the dress. It will be on display at Sotheby's global headquarters in New York from December 2 to December 8. Earlier, from September 18, the dress will be exhibited in London during London Fashion Week.

IMAGE1 Princess Diana arriving at the Serpentine Gallery in a black gown by Christina Stambolian.