The Duchess of Cambridge has gone into labour.
The child will be the Duchess and her husband Prince William's third.
The couple, who married in 2011, has two other children: Prince George, four, and two-year-old Princess Charlotte. Both were born at the same hospital, as were William and his younger brother Harry.
"Her Royal Highness The Duchess of Cambridge was admitted to St. Mary’s Hospital, Paddington, London earlier this morning in the early stages of labour," the palace said on Twitter.
"The Duchess travelled by car from Kensington Palace to the Lindo Wing at St. Mary’s Hospital with The Duke of Cambridge."