Louis Arthur Charles was born in the private Lindo Wing of St Mary's Hospital in Paddington, London, on 23 April.
The Duke and Duchess will also pay a visit to the Famine Memorial, where they'll pay their respects, before visiting the Irish Emigration Museum. It will be a busy week, however, for her brother-in-law Prince Harry and new wife Meghan Markle, who were typically affectionate at today's ceremony before their whirlwind trip to Dublin tomorrow.
Unlike the christening, which The Queen didn't attend, Her Majesty led the pack today, followed by Prince Charles and Camilla, William and Kate, and Harry and Meghan, as well as more of the royal lot.
Archbishop of Canterbury Justin Welby, the spiritual leader of the world's Anglicans, will lead the service in the Chapel Royal at St James's Palace.
Eight boys rescued from cave in northern Thailand
On Monday, a witness revealed that the fifth boy was brought out of the flooded cave at around 4.30 p.m. local time (via CNN ). Around 20 Australians have been involved in rescue efforts to free 12 boys and their soccer coach from a Thai cave.
The Queen, who didn't attend the christening of Prince Louis, appeared to be in high spirits at the RAF celebration.
While attending Prince Louis' christening, big sister Princess Charlotte gave photographers a sassy message and a stare-down. Prince William wore a sharp blue suit and was hand-in-hand with George and Charlotte who wore a white short set and blue and white printed dress respectively. And Louis' non-royal godparents will have influence on the little prince. That gown was worn for all Royal Christenings, including The Queen, her children, and seven of her eight grandchildren.
The Duke and Duchess of Cambridge also announced their youngest son's godparents a few hours before the service.
Nicholas van Cutsem: He is a British Army major and a close friend of both Prince William and Harry.
So you can only imagine my glee at seeing all the pics from the christening of Prince Louis of Cambridge.
They include the Duchess' cousin Lucy Middleton and Guy Pelly, a childhood friend of William's.