Princess Eugenie and Jack Brooksbank are expecting a baby early next year, Buckingham Palace has announced.
A tweet from the Royal Family account said the couple were "very pleased" to announce the news.
It added: "The Duke of York and Sarah, Duchess of York, Mr and Mrs George Brooksbank, The Queen and The Duke of Edinburgh are delighted with the news."
The tenth in line to the throne married Mr Brooksbank at St George's Chapel in Windsor Castle in October 2018.
Posting a photo of herself and her husband on Instagram alongside another of some baby shoes, the princess said the couple were "so excited".
Messages of congratulation for the expectant parents have included one from Prime Minister Boris Johnson.
The couple's baby will be the Queen and the Duke of Edinburgh's ninth great-grandchild. Their eighth - the Duke and Duchess of Sussex's son, Archie Mountbatten-Windsor - was born last May.
Eugenie's parents, Prince Andrew and Sarah, Duchess of York, will become grandparents for the first time.
The baby boy or girl will be born 11th in line to the throne.
Because the child will be born down a female line of the Royal Family - and drinks executive Mr Brooksbank has no royal status - he or she will be plain Master or Miss Brooksbank, with no royal title.
This could change if the Queen decided to give Mr Brooksbank an earldom or issue Letters Patent to amend the rules.
Princess Eugenie and Mr Brooksbank - who is European brand manager for Casamigos Tequila, co-founded by George Clooney - met when skiing in Switzerland in 2010.
Their wedding was watched on an extended episode of ITV's This Morning by an average of three million people, giving the channel its best ratings for the timeslot since William and Kate's marriage in 2011.
Celebrities including Cara Delevingne and Robbie Williams were among the 850 guests, with an additional 1,200 members of the public invited to follow proceedings from the grounds.
Princess Eugenie's wedding dress - designed by Peter Pilotto and Christopher De Vos - featured a low back, at her request, to show a scar from surgery she had to correct scoliosis when she was 12.
The Duke and Duchess of Cambridge's children, Prince George and Princess Charlotte, acted as pageboy and bridesmaid.
Eugenie's sister, Princess Beatrice, married her property tycoon Edoardo Mapelli Mozzi, at a small private ceremony in Windsor in July. She had been due to marry in May but coronavirus delayed the plans.