Although Prince William and Duchess Catherine were on their tour of India and Bhutan earlier this month, the party planning for the special day, May 2, has no doubt been in full swing for a while.
"Normally for a high-profile kids birthday, the invite goes out six months prior to the event," Sarah Dixon, a maternity nurse who has worked for friends of the royal couple, tells WHO. "These people have busy diaries!"
So what sort of celebration will the royal couple have planned for their little princess?
"I think they will definitely have some sort of theme, maybe something gender-neutral like animals or pretty gingham cotton bunting with elegant lunch settings and canapés for the adults," says Dixon, noting that an outdoor setting is often best, especially for rambunctious two-year-olds like big brother Prince George.
And of course, we're sure that Kate's mom, Carole Middleton, founder of the online kids' party supplier firm Party Pieces, has been more than happy to pitch in with ideas. "Whether you decide to keep it small and intimate or opt for a much bigger gathering, your little ones first birthday is certainly something to celebrate," she wrote last May in Baby London magazine.
And when it comes to themes, one of Middleton's favourites is a classic. "Beatrix Potter’s characters are timeless and perfect for both boys and girls," advised Charlotte's grandma, adding, "a theme can be an effective way to personalize a party."
While Kate is no doubt taking the lead when it comes to all things party-related for Charlotte's big day on May 2, she'll be sure to have at least one other little helper. "George will enjoy all the birthday festivities, and I'm sure there will be a few of his friends invited too," says Dixon. "He'll help Charlotte open all her gifts – older siblings love to do that!"
Likely to take place at their country residence of Anmer Hall in Norfolk, which is where the family are primarily based, the party will be the perfect excuse for the couple to have a catch up with friends post-tour.
The littlest royal stole the show in a recent portrait for her great-grandmother's 90th birthday.
Occupying a place of honour in Queen Elizabeth's lap – befitting a tradition of royal portraiture – Charlotte poses alongside her big brother and royal cousins. (With their matching pink cardigans and blue eyes, the two make a strong bid for royal twinning!)