The new-born, whose name has not yet been announced, is now fifth in line to the throne, after his grandfather Prince Charles, his father Prince William, his brother Prince George and his sister Princess Charlotte.
In a statement Kensington Palace said: “Her Royal Highness The Duchess of Cambridge was safely delivered of a son at 1101hrs.
“The baby weighs 8lbs 7oz. The Duke of Cambridge was present for the birth. Her Royal Highness and her child are both doing well.
“The Queen, The Duke of Edinburgh, The Prince of Wales, The Duchess of Cornwall, Prince Harry and members of both families have been informed and are delighted with the news.”