A Buckingham Palace statement said: "Her Royal Highness The Duchess of Sussex was safely delivered of a son at 0526hrs.
"The baby weighs 7lbs 3oz.
"The Duke of Sussex was present for the birth.
"The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, The Duke and Duchess of Cambridge, Lady Jane Fellowes, Lady Sarah McCorquodale and Earl Spencer have been informed and are delighted with the news.
"The Duchess's mother, Doria Ragland, who is overjoyed by the arrival of her first grandchild, is with Their Royal Highnesses at Frogmore Cottage.
"Her Royal Highness and her child are both doing well."
The name of the baby, which is seventh in line to the throne, will be announced at a later date.
The Duke of Sussex announced the birth of the new royal baby.
Speaking from Windsor, Prince Harry said: "I'm very excited to announce that Meghan and myself had a baby boy this morning, a very healthy baby boy.
"It's been the most amazing experience I could ever have possibly imagined.
"How any woman does what they do is beyond comprehension. But we're both absolutely thrilled.
"We're both absolutely thrilled and so grateful for all the love and support from everybody out there, it's been amazing, so we just wanted to share this with everybody."
The duke and duchess's Instagram account @SussexRoyal also announced the birth saying: "It's a boy! Their Royal Highnesses the Duke and Duchess of Sussex are overjoyed to announce the birth of their child."