Royal fans were delighted as Kensington Palace shared a new photograph to mark the Princess of Wales's 43rd birthday on Thursday.
The black and white portrait, taken by photographer Matt Porteous in Windsor last summer, showed Kate dressed smart-casually, posing with her hands in the pockets of her jeans.
Accompanying the image was an emotive personal message from the Prince of Wales, who penned: "To the most incredible wife and mother. The strength you've shown over the last year has been remarkable. George, Charlotte, Louis and I are so proud of you. Happy Birthday, Catherine. We love you. W."
The new photo and William's heartfelt tribute sparked a huge reaction from royal fans in the comments on social media, with many praising the Prince for his personal words.
"The sweetest message from the sweetest husband. Happy birthday Princess!!" one wrote.
"This is the sweetest message of a very proud husband. Happy Birthday, Catherine," a second said.
A third added: "That’s such a lovely message! Also beautiful photo. Wishing the happiest of birthdays to The Princess of Wales."
It marked a rare personal message from the Prince, who previously described the past year as "brutal" amid his wife's abdominal surgery and cancer diagnosis – with his father, King Charles, also undergoing his own cancer treatment.
Opening up about her cancer journey at her Christmas concert in December, Kate said: "I didn’t know this year was going to be the year that I've just had."
She also told well-wishes on the Christmas Day walkabout in Sandringham that she was "hugely grateful" for health workers.
As Kate walked back to Sandringham House after the church service, one woman who had worked for Macmillan Cancer Support told the Princess that she is an "inspiration to all patients".
Appearing deeply touched by her comment, Kate responded: "The amount of people who have written this year is extraordinary and I think cancer just really does resonate with so many families."
Gesturing to the healthcare worker, the Princess added: "People like you are doing all the hard work out there. I'm hugely grateful."
Kate, who celebrated her birthday privately in Windsor with her family, is making a gradual return to her public duties after completing chemotherapy last autumn.
In the video montage to announce the end of her treatment, the Princess said: "The last nine months have been incredibly tough for us as a family. The cancer journey is complex, scary and unpredictable for everyone, especially those closest to you."
Kate added: "Doing what I can to stay cancer free is now my focus. Although I have finished chemotherapy, my path to healing and full recovery is long and I must continue to take each day as it comes."