PRINCE William has shared a poignant message to Kate wishing a Happy 43rd Birthday to "the most incredible wife and mother".
Wills, 42, marked Kate's special day with an unprecedented personal post and hailed her unwavering "strength".
The proud husband paid the royal mum-of-three a Happy Birthday after a turbulent 12 months for their family.
He wrote: "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"
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William also shared an unseen black and white picture of the Princess.
It was taken by photographer Matt Porteous and shows Kate standing tall, but looking relaxed, in Windsor last summer.
The royal opted for a laid back white blouse, blue jeans, black blazer, accessorized with a gingham scarf.
She is beaming in the gorgeous snap, with her hands casually resting in her pockets.
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Her hair is elegantly styled with loose curls, paired with simple looking makeup to enhance her natural beauty.
The Prince will be celebrating Kate's birthday with her and their three children, George, 11, Charlotte, nine, and six-year-old Louis in Windsor today.
It comes after the King led well-wishes on social media earlier this morning.
King Charles and Queen Camila shared on X: "Happy Birthday to The Princess of Wales!"
The Monarch, 75, shared a picture of Kate attending the Royal Family's traditional Christmas Day service at St Mary Magdalene Church in Sandringham, Norfolk, last year.
Royal fans also inundated the mum-of-three with sweet well wishes.
One wrote: "I love the princess of Wales so much. She is an angel."
Another penned: "Happy birthday to the beautiful princess."
"Wishing Catherine the happiest of birthdays today. May today and the next year be wonderful for her. Much love to the Princess," shared a third.
It comes as Kate marks a gradual return to work following a turbulent past 12 months.
William described 2024 as a "brutal" and probably "the hardest year" of his life, with his father, the King, also diagnosed with cancer.
Next week will mark a year since the princess was admitted to hospital for an operation on January 16, just seven days after her 42nd birthday.
She spent nearly two weeks in the London Clinic after major abdominal surgery, before beginning chemotherapy.
Since then, the 43-year-old has remained largely out of the public eye.
But, she announced in September last year that her had finished chemotherapy and she would focus on being "cancer free" in a heartwarming video.
By the end of 2024, the Princess made more appearances including hosting her annual Together at Christmas carol service at Westminster Abbey.
And that gradual return continues in 2025 — although fans have been warned not to expect Kate to be “rushing back to the same volume of work” as before.
It is also understood tours abroad are “not on the table”, despite Prince William last year saying they might “have some more trips lined up”.
Instead, Kate’s “primary focus” will be her Centre for Early Childhood and UK-based engagements. She is expected to be seen “up and down the country” this year.
She will also support the Royal Family at events such as Buckingham Palace Garden Parties, Trooping the Colour, Royal Ascot and the Remembrance Day commemorations.
A source said: “There is no huge reset button on her work and if you look to the back end of 2024 there was a gradual return of the Princess of Wales into more public engagements.
“That gradual return will continue into 2025 and it was an extremely warm and wonderful bookend to 2024 to see her at the carol service, and she continues that gradual return.”
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Kensington Palace is working on her 2025 programme, which “balances work, being a mum and supporting her wider family” and public-facing engagements will continue this year.
A source said: “It would be wonderful to see the Princess of Wales up and down the country and this year I’m sure that will be the case."