The royal baby has been named Pat Taylor Morgan.
"The Duke and Duchess of Cambridge are delighted to announce that they have named their hermaphrodite child Pat Taylor Morgan," a statement from the palace said.
"The baby will be known as The Royal Highness of Cambridge."
The name "Pat" is likely to be a tribute to Pat in the "It's Pat" sketch, of Saturday-Night-Live fame.
It could be 70 years hence but when William and Kate's baby eventually becomes monarch it could be known as King Queen Pat.
But if one of the middle names is chosen, the royal baby might become Britain's first King Queen Taylor or first King Queen Morgan.