Meghan Markle, the Duchess of Sussex, has given birth to a baby boy with Prince Harry by her side.
The official Instagram account for the Duke and Duchess of Sussex carried the happy news.
The new royal was born in the early hours of Monday, May 6, weighing 7lbs 3oz.
The Duke and Duchess say they are "overjoyed".
Mother and baby are doing well, Buckingham Palace confirmed, adding that more details will be released in due course.
News first broke that the Duchess had gone into labour on Monday.
"The Duchess went into labour in the early hours of this morning," a Royal Communications circular read. "The Duke of Sussex was by her Royal Highness's side. An announcement will be made soon."
Prince Harry was pictured looking overjoyed following the birth of his first child, and added the couple were still thinking of a name for their new arrival.
"It's been the most amazing experience I could ever have possibly imagined," he told waiting reporters outside his Windsor home. "How any woman does what they do is beyond comprehension. I'm so incredibly proud of my wife."
The baby is the seventh-in-line to the British throne, behind Prince Charles, Prince William, William’s three children and Prince Harry, the Duke of Sussex.
A notice of birth was placed on display on a ceremonial easel outside Buckingham Palace.
Breaking with tradition, the Duke and Duchess said earlier in April that they would keep the birth private until they had "celebrated as a family".
The Duchess of Cambridge, Princess Diana and Princess Anne had all of their children at the Lindo Wing of St Mary's Hospital in Paddington, central London, posing outside for photographs hours after giving birth.
But reports circulating before the birth suggested that Meghan chose a maternity wing at a hospital closer to her home in Frogmore Cottage in the county of Berkshire, south of London.
Queen Elizabeth II is thought to have been the first person to be informed when the baby was born and to discover the gender.
The British monarch also has the power of veto over the Sussexes' choice of baby name, although it is unlikely she would ask the couple to change the name.
Alexander and Philip, the name of Harry’s grandfather, are the favourites for a baby boy.
Meghan, 37, announced in October last year that she was expecting her first child with Harry in spring 2019.
Although the Sussexes did not confirm an exact due date, the Duchess let slip at an event earlier this year that she was expecting to give birth in April.
Sussex Royal launches online
Before welcoming their new arrival, the Duke and Duchess of Sussex officially launched the Sussex Royal Instagram page. The account got over 300,000 followers in its first hour.
"Welcome to our official Instagram," Harry and Meghan wrote. "We look forward to sharing the work that drives us, the causes we support, important announcements, and the opportunity to shine a light on key issues. We thank you for your support, and welcome you to @sussexroyal."
The caption accompanied a gallery of 10 images, beginning with one of their joint monogram, followed by a series of images from their 11 months of marriage. Some of the photos were previously unseen images of the couple.
The shared photos include, sailing in Sydney Harbour, Meghan embracing women at the launch of the Hubb Community Kitchen charity cookbook and Harry on a wildlife reserve in Malawi.
Run-up to the birth
Meghan made her last public appearance in March when she visited New Zealand's High Commission in London to pay tribute to the victims of the Christchurch terror attack.
Earlier that month she spoke at a panel event to mark International Women's Day where she said she hoped her unborn baby would be a feminist.
Meghan celebrated the impending birth with a lavish baby shower in New York, which is believed to have been thrown by her close friends Amal Clooney and Serena Williams.
The former actress, who became famous for starring in Netflix legal drama Suits, married Harry in May last year at a ceremony at Windsor Castle.
The couple met after being set up on a blind date by a “mutual friend”, believed to be Bahrain-born fashion designer Misha Nonoo.