The Duchess of Sussex, Meghan, has given birth to a boy described by Prince Harry as "'absolutely to die for".
The so far unnamed boy, the seventh in line to the throne, was born in the early hours of Monday UK time weighing 3.26 kg.
Meghan and the baby were both healthy and well, Buckingham Palace said in a statement.
"How any woman does what they do is beyond comprehension but we're both absolutely thrilled and so grateful to all the love and support from everybody out there," a smiling Prince Harry told reporters in Windsor, west of London, where the couple live.
"It was amazing, absolutely incredible. As I say, I am so incredibly proud of my wife and, as every father and parent would ever say your baby is absolutely amazing, this little thing is absolutely to die for."
Harry and Meghan's mother Doria Ragland were present for the birth at at the couple's home Frogmore Cottage, on the Windsor Castle estate where they married in a lavish ceremony in May last year.
The baby is the eighth great-grandchild of the 93-year-old Queen, the world's longest-reigning monarch, and could be entitled to hold joint British and US citizenship according to nationality rules.
However the child will not automatically be a prince or a princess and any such title would have to be bestowed by the Queen by issuing what is known as a letter patent.
The Queen and other members of the royal family, including Harry's aunt and uncle - Princess Diana's sister and brother - were delighted by the news of the birth, the palace said.
The baby is the first mixed race baby born into a senior position in British royalty, according to royal experts.
Harry and Meghan used their official Instagram account to announce the birth, in modern fashion.
But in accordance with a tradition dating back at least to 1837 when Buckingham Palace became the sovereign's official residence, some hours later a notice announcing the birth was posted on a ceremonial easel on the forecourt of Buckingham Palace.
The palace did not confirm whether Meghan gave birth at home. While the late Princess Diana gave birth to Harry and his older brother William in hospital, the Queen's four children were all born at Buckingham Palace.
James, Alexander, Albert, Philip and Arthur are among the favourite names for the child, according to bookmakers.
"We're still thinking about names," Prince Harry said.
"The baby's a little bit overdue so we've had a little bit of time to think about it ... that's the next bit."
Meghan's estranged father Thomas Markle said he was delighted at the news.
"I am proud that my new grandson is born into the British royal family and I am sure that he will grow up to serve the crown and the people of Britain with grace, dignity, and honour," he said in a statement to the Sun newspaper.
Australian Associated Press
