The image was taken by Prince William earlier this week. It is something of a role reversal for the couple, who traditionally issue images taken by the princess as she is a keen photographer.
The picture, part of the family’s annual tradition of posting a message for Mother’s Day, will go some way to answering questions from the public about the princess’ wellbeing.
Kensington Palace has always reiterated that she has been “doing well” following major abdominal surgery in January, recuperating slowly at home in Adelaide Cottage with her young family.
She has not appeared in public since Christmas Day, but was photographed by paparazzi being driven by her mother in Windsor last week.
The question of “Where is Kate?” had travelled around the world on social media, accompanied by increasingly outlandish conspiracy theories.
Buckingham Palace has also shared a photo of the King with his late mother Queen Elizabeth II in a post online to mark Mothering Sunday.
The picture shows King Charles, then Prince of Wales, in 1985 kissing the hand of his mother at a presentation ceremony after a polo match.
Alongside the photo is a pink flower emoji and the message: “Wishing all Mothers, and those who are missing their Mums today, a peaceful Mothering Sunday.”
In the match at the Guards Polo Club in Windsor Great Park, Charles’ England II team triumphed against Brazil to claim the Silver Jubilee Cup.
In recent years, the Prince and Princess of Wales have authorised photographs of their family to be shared with the public to mark Mothering Sunday.
Last year, they used an image from a set taken months earlier showing the three children climbing a tree.
In other years, they have shared images of handmade cards from George, Charlotte and Louis.
