Princess Eugenie will invite 1,200 members of the public to her wedding.
The 28-year-old royal - who is the daughter of Queen Elizabeth's son Prince Andrew and his ex-wife Sarah Ferguson - will marry Jack Brooksbank at St. George's Chapel in Windsor Castle on October 12 and the couple are launching a public ballot, which will see successful applicants invited into the grounds to be a part of the celebration.
A Buckingham Palace statement announced: "The couple are delighted to announce an opportunity for 1,200 people from across the United Kingdom to be invited into the grounds of Windsor Castle to share the experience of their special day.
"The attendees will view the arrival of the congregation and Members of the Royal Family, listen to a live broadcast of the Marriage Service and watch as the Bride and Groom depart St George's Chapel at the end of the ceremony."
Invitees to the castle grounds will also include members of the local community, children from the schools attended by the princess, royal household staff and representatives of charities supported by Eugenie and Jack.
As when Eugenie's cousin, Prince Harry, married Meghan, now Duchess of Sussex, in May, the happy couple will undertake "a short carriage procession" through Windsor High Street after exchanging their vows.
An online application form to attend the nuptials is open until August 8, and one person can request spaces for up to four people, so long as they live at a UK or British Forces postal address and are over five years old.
Successful applicants will be issued entry cards, which are not transferable and the lucky invitees will be required to bring photographic identification and proof of address with them on the day.
It was previously claimed Robbie Williams and Ayda Field's five-year-old daughter, Teddy, will be one of the flower girls at the couple's wedding, alongside Prince William and Duchess Catherine's daughter Princess Charlotte, three, and four-year-old Maud Windsor, who is the daughter of Lord Freddie Windsor and his wife, actress Sophie Winkleman.
A source said: "This is a great moment for Robbie. He couldn't be more proud for his daughter."
Charlotte's brother, five-year-old Prince George - who is in the same class as Maud at St Thomas' School in Battersea - will be a pageboy at the wedding, as will Louis de Givenchy, the son of the banker Olivier de Givenchy and his wife Zoe.