“Her Royal Highness Princess Beatrice and Mr Edoardo Mapelli Mozzi are very pleased to announce that they are expecting a baby in autumn of this year,” the palace said in a statement.
“The Queen has been informed and both families are delighted with the news.”
The 32-year-old is the elder daughter of Prince Andrew and Sarah, Duchess of York, and the granddaughter of Queen Elizabeth II.
The queen currently has 10 great grandchildren, with two new royal arrivals this year – Beatrice’s sister Eugenie had her first baby in February and Zara Tindall, the daughter of Princess Anne, gave birth to her third child in March.
Prince Harry and his wife Meghan are also expecting their second child this year.
Beatrice, who is ninth in line to the throne, is not a full-time working royal but is employed by Afiniti, an artificial intelligence software firm, where she is vice president of partnerships and strategy.
Mapelli Mozzi is the son of former Olympic skier Count Alessandro Mapelli Mozzi and Nikki Williams-Ellis and is a count himself.
He already has a young son named Wolfie with ex-fiancee Dara Huang.