Many of the gowns will already be familiar to millions after being captured in images of one of the most photographed women in the world.
Among the 10 cocktail frocks, ballgowns and formal evening dresses that are up for sale is the Victor Edelstein gown she wore when she danced with John Travolta at a glitzy White House state dinner.
The image of the Princess in the striking off-the-shoulder midnight blue velvet dress and sapphire and diamond choker, dancing and twirling around with the Hollywood heartthrob captivated the US when she and the Prince of Wales visited in 1985.
The dress, which is expected to fetch between £200,000 and £300,000, was previewed today along with the others ahead of the sale at Kerry Taylor Auctions in London on March 19.
The items were originally sold at auction along with a number of others by Diana herself to raise money for charity at the suggestion of her son, the Duke of Cambridge, following her divorce from Prince Charles.
One of the buyers, American Maureen Rorech Dunkel, initially bought the 10 dresses as a long term investment, but after Diana's death in 1997 she decided to exhibit them to raise money for good causes.
They are now being sold by an anonymous seller.
Among the other dresses in the Fit For a Princess collection is a Catherine Walker Mughal-inspired embroidered pink slubbed silk evening gown and bolero which was made for Diana and Charles's state visit to India in 1992, which is expected to be sold for up to £120,000.
It was on this trip that the famous photograph of the Princess sitting alone outside the Taj Mahal was taken.
It is one of six dresses by Walker - one of the Princess's favourite designers - up for sale.
Another by the French-born dressmaker is a burgundy velvet gown with embroidered tailcoat, which was worn during a State visit to Korea in 1992 and to the premiere of Steel Magnolias two years earlier. It is expected to fetch up to £60,000.
A Walker black velvet and beaded evening gown, which Diana was photographed in by Mario Testino for a Vanity Fair photoshoot just a few months before she died is also part of the collection with a guide price of £50,000 to £70,000.
It is the only one of the 10 to have been worn after her divorce from Charles.
A dress by another of her favourite designers, Bruce Oldfield, also features.
The black velvet evening gown was worn for an official portrait by Lord Snowdon and at the gala opening of Les Miserables in 1985 and is expected to fetch up to £50,000.
Auctioneer Kerry Taylor said: "It's probably the last time that these 10 Diana dresses will be seen together because after the auction obviously, they'll probably be scattered across the world.
"In a way it's like a little history of Diana's life through her clothes."
Ms Taylor said that most of the interest so far had been from the US.
But she added: "She wore these clothes in Brazil, in Australia, in South Korea, in Austria, as well as obviously here and it will be interesting to see if we get buyers from those places."
In 2010 a black taffeta dress worn by Diana on her first official engagement with her then fiance Charles in 1981 was sold for £192,000 by the specialist vintage fashion auctioneers, which is based in Bermondsey, south east London.
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