Princess Eugenie is to marry her long-term boyfriend Jack Brooksbank - at the same wedding venue as Prince Harry and Meghan Markle.
The Queen's granddaughter will wed Mr Brooksbank in St George's Chapel in Windsor Castle in the autumn next year.
Buckingham Palace said Eugenie's parents, the Duke of York and his former wife Sarah Duchess of York, were delighted to announce the engagement.
The pair became engaged in Nicaragua earlier this month, the palace revealed.
Eugenie, 27, began dating Mr Brooksbank around seven years ago after they met while skiing in the Swiss resort of Verbier.
The Stowe-educated socialite is the manager of Mayfair hotspot Mahiki.
Harry and Ms Markle are marrying in St George's Chapel May.
In a statement, Buckingham Palace said: "The Duke and Duchess of York are delighted to announce the engagement of Princess Eugenie to Mr Jack Brooksbank.
"Her Royal Highness and Mr Brooksbank became engaged in Nicaragua earlier this month.
"The wedding will take place in the Autumn of 2018 at George's Chapel in Windsor, with further details to be announced in due course."
Nicola and George Brooksbank, the parents of Eugenie's fiance Jack Brooksbank, have spoken of their joy about the couple announcing their plans to wed.
The couple said in a brief statement: "We could not be more delighted with the news of the engagement.
"We are completely over the moon and are very excited for them both."
In three tweets - which were retweeted by the Duke of York - Sarah Duchess of York expressed her happiness at the news.
In the first, she wrote: "Total joy!! #engagement @TheDukeOfYork" and included a picture of the couple overlaid with the words: "A total embrace of goodness and joy. We love Jack and I am so excited to have a son, a brother and a best friend. Eugenie is one of the finest people I know and so together it will be pure harmony."
In another, which had another picture of the couple on a boat, she wrote: "They float with laughter and love .. although a boat helps! #engagement #eugieandjack @TheDukeOfYork @yorkiebea".
And in a third: "I always say that the river flows well to it's destiny because of the guidance of a solid rock #engagement #eugieandjack @TheDukeOfYork @TheDukeOfYork".