The world finally caught a glimpse of the new prince when the Duke and Duchess of Cambridge emerged from St Mary's Hospital carrying their tiny bundle of joy.
The Duchess, Kate Middleton, was all smiles as she cradled the new prince of Cambridge on the steps of the Lindo Wing, less than seven hours after giving birth.
Kate was dressed in patriotic colours - wearing a red Jenny Packham shift dress with a white floral lace collar - as she made her first public appearance with her St George's Day baby.
The prince, whose name has not yet been announced, was wrapped in a lace shawl with a matching bonnet.
The Duchess went into labour this morning.
The news was confirmed in a tweet by Kensington Palace.
Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 1101hrs.
— Kensington Palace (@KensingtonRoyal) April 23, 2018
The baby weighs 8lbs 7oz.
The Duke of Cambridge was present for the birth.
Her Royal Highness and her child are both doing well.
Kensington Palace said the Queen, Duke of Edinburgh, Prince of Wales, Duchess of Cornwall, Prince Harry and members of both families are "delighted with the news."
The Duchess and Prince William already have two children - Prince George, four, and Princess Charlotte, two.
Emulating the birth pattern of the Queen and Prince Philip's first three children, William and Kate have had a son, a daughter and now another son.
The arrival of a prince was a surprise for the Duke and Duchess, who chose not to find out the sex of their baby in advance.
The royal baby has been born on patriotic St George's Day, which celebrates the patron saint of England.
Like George, the baby is a Prince of Cambridge. He is born fifth in line to the throne.
Kensington Palace said the name of the baby would be announced in due course, and a formal notice of the birth would be posted on the forecourt of Buckingham Palace.
Celebrities and politicians have been sending their best wishes on social media.
Prime Minister Theresa May sent her "warmest congratulations to the Duke and Duchess of Cambridge on the birth of their baby boy."
"I wish them great happiness for the future," she added.
Mayor of London Sadiq Khan tweeted: "On behalf of Londoners, I want to send our warmest congratulations to the Duke and Duchess of Cambridge on the birth of their baby boy."
Former world heavyweight champion boxer, Frank Bruno MBE, and Hollywood actress Mia Farrow were among the celebrity well wishers on social media.
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