The Duke and Duchess of Cambridge's son was born at 4.24pm, Monday, July 22.
Prince William had said the couple "could not be happier" following the birth of the 8lb 6oz boy.
Gun salutes in Green Park and the Tower of London and the ringing of bells at Westminster Abbey have marked the birth of the third in line to the throne.
The King's Troop Royal Horse Artillery fired a 41-gun salute in Green Park at 14:00 BST, after riding past Buckingham Palace.
At the same time, the Honourable Artillery Company - the City of London's army reserve regiment - fired a 62-gun salute from Gun Wharf at the Tower of London.
Visitors to Niagara Falls discovered the baby's gender in spectacular fashion as the rapids turned blue.
God bless the Royal Family!