Catherine, Princess of Wales announced Monday that she was cancer-free but on a long road to "full recovery", in a highly emotional video message following a shock cancer diagnosis earlier this year.
The heartfelt announcement will provide welcome relief for Britain's royal family after a troubled year in which head of state King Charles III also revealed he was battling cancer.
"I cannot tell you what a relief it is to have finally completed my chemotherapy treatment," Kate, as she is often called, said in a message on X and Instagram.
The princess, 42, said the last nine months had been "incredibly tough" for the family -- her husband Prince William and their children Prince George, 11, Princess Charlotte, nine, and Prince Louis, six.
"Life as you know it can change in an instant and we have had to find a way to navigate the stormy waters and road unknown," she said.
Catherine, a future queen seen as a key figure to maintain the royals' position in a changing Britain, added that "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," she said.
"I am however looking forward to being back at work and undertaking a few more public engagements in the coming months when I can."
Catherine announced in March that she was undergoing a course of "preventative chemotherapy" for an undisclosed cancer.
- Solidarity -
The announcement came just weeks after it was disclosed that her father-in-law had also been diagnosed with cancer after undergoing treatment for a benign prostate.
Charles, 75, was given the green light to resume public duties in April after doctors said they were "very encouraged" by his progress.
He was seen on Saturday with his wife Queen Camilla and other members of the royal family at the Braemar Gathering Highland Games, and attended a church service to mark the second anniversary of his accession to the throne.
Monday's video message shows Catherine and William looking relaxed and happy with their children in the Norfolk countryside and at the beach in eastern England where they have a home.
The couple are seen being openly affectionate to one another with William at one point planting a kiss on Catherine's cheek.
In other scenes, the family is seen walking through woodland, having a picnic and playing cards.
The video was filmed last month, their Kensington Palace office said.
Catherine added that the months since her diagnosis had "above all reminded William and me to reflect and be grateful for the simple yet important things in life, which so many of us often take for granted. Of simply loving and being loved."
And she expressed solidarity with fellow cancer sufferers.
"To all those who are continuing their own cancer journey -- I remain with you, side by side, hand in hand. Out of darkness, can come light, so let that light shine bright," she said.
Catherine has appeared in public on only a handful occasions this year.
- Tentative return -
When she announced her cancer diagnosis in a video on March 22 she had not been seen in public since Christmas.
The disclosure came after royal officials said in January that Catherine would spend two weeks in hospital for abdominal surgery.
Catherine tentatively returned to UK public life in June, attending a military parade in London to officially mark Charles's birthday.
In July, she attended the Wimbledon men's tennis final at which she received cheers as she walked onto court to present the trophy to Carlos Alcaraz.
Cancer charities welcomed Catherine's announcement.
Laura Lee, chief executive of Maggie's charity, which supports cancer patients and their families, said it was "fantastic news".
"It will benefit so many people living with cancer to see her come through treatment and share this video," she said.
A spokesperson for Macmillan Cancer Support said her decision to be "so open about her experience" would "give hope to many others going through similar experiences".
The royal family has endured a turbulent few years.
Queen Elizabeth II died in September 2022 after 70 years on the throne less than 18 months after the death of her husband Prince Philip.
Prince Harry, Charles's younger son, meanwhile, sensationally quit royal life in 2020 and settled in California in the United States with his wife Meghan.
They grabbed headlines worldwide by complaining bitterly about their treatment in the UK in an interview with chat show queen Oprah Winfrey, in a Netflix series and in Harry's blockbuster autobiography "Spare".
The string of negative attacks has left Harry largely estranged from most of the royal family, especially his brother William, although there has been something of a rapprochement with his Charles since his cancer diagnosis.