Adelaide is 15th in line to the British throne, following her two brothers.
Prince Edward, Duke of Edinburgh, consequently moves one place lower in the succession.
Her arrival comes during continuing controversy surrounding Eugenie’s father, Andrew Mountbatten-Windsor, 66, who was stripped of his prince title and HRH style in 2025.
Eugenie has maintained an independent public profile through her work as a director at contemporary art gallery Hauser and Wirth and as co-founder of The Anti-Slavery Collective with Julia de Boinville.
Buckingham Palace formally announced Adelaide’s arrival on August 4, confirming Charles, 77, Queen Camilla, 79, and other relatives had been informed.
The Palace said: “Her Royal Highness Princess Eugenie and Mr Jack Brooksbank are delighted to announce the safe arrival of their daughter, born on Monday, 3rd August 2026, at 6:20 pm, at a hospital in Lisbon, Portugal.”
Eugenie’s scandal-plagued dad, Andrew, was released “under investigation” earlier this year after being arrested on suspicion of misconduct in public office after allegedly sharing sensitive information with his predator friend Jeffrey Epstein during his role as a trade envoy for Britain, but he denies wrongdoing.