On 17 July 2020, Princess Beatrice and Mr Mapelli Mozzi were married at the Royal Chapel of All Saints in Windsor.
The garment will be displayed at Windsor Castle from 24 September 2020 until 22 November 2020, the Royal Collection Trust said.
Made from peau de soie taffeta, the garment was originally worn by the monarch in the 1960s.
Queen Elizabeth II first wore the gown in 1961 for a state dinner at the British Embassy in Rome.
She wore it twice more, at the world premiere for Lawrence of Arabia at the Odeon Leicester Square in December 1962, and during the State Opening of Parliament in 1966.
It is embellished with hand-embroidered crystals and diamantes, with ivory duchesse satin on the trim of the skirt.
For Princess Beatrice’s wedding, the Queen’s personal adviser and dresser Angela Kelly and fashion designer Stewart Parvin worked together to make alterations to the dress for the bride.
In addition to her wedding gown, Princess Beatrice’s Valentino wedding shoes will also be displayed at Windsor Castle.
A replica of her bridal bouquet, made with artificial flowers, will also be shown at the exhibition.
Princess Beatrice and Mr Mapelli Mozzi had a small wedding ceremony, with the Queen, the Duke of Edinburgh and the bride’s parents, the Duke and Duchess of York, in attendance.
Buckingham Palace stated that all guests at the secret wedding adhered to strict social distancing guidelines.