It's her third child - so she's had practice (and form!) when it comes to dressing for a high-profile christening.
And the Duchess Of Cambridge certainly didn't disappoint on Monday for Prince Louis's big moment.
The 36-year-old wore a white dress by Alexander McQueen - one of her favourite labels and the same designer that created her breathtaking 2011 wedding gown.
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Kate furthermore once again opted for white; the same shade she wore for both George and Charlotte's christenings in 2013 and 2015 respectively.
Her headpiece was also fab; it was created by Jane Taylor.
Meanwhile, Meghan went for an off-green Ralph Lauren along with a hat by Stephen Jones. The Duchess of Cornwall chose a Fiona Clare dress and a Locke hat.
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Pippa Matthews - Kate's 33-year-old sister - is currently expecting her first child. She wore blue Alessandra Rich as she arrived with her cousin, Lucy Middleton.
Prince George and Princess Charlotte as always looked completely adorable - not to mention very well-behaved.
The Archbishop of Canterbury was on hand to baptise 11-week-old Prince Louis on Monday.
He was supported by The Dean of The Chapel Royal, The Right Reverend and Right Honourable the Lord Chartres, and The Sub-Dean of the Chapel Royal, The Reverend Canon Paul Wright.
A statement on Monday announced the godparents as:
- Mr Nicholas van Cutsem - a close friend of Prince William who also accompanied the Duke and Duchess of Cambridge's carriage at their wedding
- Mr Guy Pelly - longtime friend to William and Kate, Pelly was responsible for William's stag party back in 2011
- Mr Harry Aubrey-Fletcher - one of William's oldest friends who asked the Prince to be an usher at his wedding
- The Lady Laura Meade - another close friend to the couple, with William also acting as usher at her wedding
- Mrs Robert Carter, Hannah Gillingham - she is an old school friend of Kate Middleton
- Miss Lucy Middleton - first cousin of Kate
