Details of the godparents are yet to be announced but it's thought Prince Harry and new bride Meghan Markle won't get called up to the duty.
Here's an understatement for you: It's been a pretty hectic year for the royal family.
This marks a return to the London location, as the couple picked St Mary Magdalene church, on the Queen's estate in Sandringham, Norfolk, for the christening of Princess Charlotte back in 2015.
Charlotte's mad about pink, he (Prince William) said it's her favourite colour.
Thursday marked the 36th birthday of the Duke of Cambridge, and the future King of England celebrated in the best way - by giving a sweet speech at a charity event.
The Duke and Duchess of Cambridge welcome their third child at the Lindo Wing, St Mary's Hospital, Paddington, London, UK.
Prince Louis will be baptised at the same place as his older brother George.
"Judging by the previous christenings, and the importance of the day for the family, Louis' christening will be a private affair, perhaps no surprise there. They give the photographers something to work with and then they expect a bit of privacy for the rest of the day".