She shared a black and white photograph on social media alongside which she wrote: "Since I was ten years old, I have loved and looked up to Olivia Newton-John. And, I always will. (Just like this picture @nfsaonline) She was, and always will be, an inspiration to me in so many, many ways. My deepest condolences to her family and loved ones. X ONJ4EVA @therealonj".
VIDEO: Olivia Newton-John gets real about her cancer diagnosis
The singer's husband, John Easterling, announced the heartbreaking news on Monday, August 8, alongside a photograph of her on Instagram and an emotional statement.
It read: "Dame Olivia Newton-John (73) passed away peacefully at her Ranch in Southern California this morning, surrounded by family and friends. We ask that everyone please respect the family's privacy during this very difficult time.
"Olivia has been a symbol of triumphs and hope for over 30 years sharing her journey with breast cancer. Her healing inspiration and pioneering experience with plant medicine continues with the Olivia Newton-John Foundation Fund, dedicated to researching plant medicine and cancer.
Kylie penned an emotional tribute
"In lieu of flowers, the family asks that any donations be made in her memory to the @onjfoundation."
It continued: "Olivia is survived by her husband John Easterling; daughter Chloe Lattanzi; sister Sarah Newton-John; brother Toby Newton-John; nieces and nephews Tottie, Fiona and Brett Goldsmith; Emerson, Charlie, Zac, Jeremy, Randall, and Pierz Newton-John; Jude Newton-Stock, Layla Lee; Kira and Tasha Edelstein; and Brin and Valerie Hall."
The Grease star passed away after a decades-long battle with breast cancer, and although she was on the road to recovery, she'd spoken about how much it affected her.
Having both risen to prominence in the 80s in the Australian and then international music scene, the two have been constantly supportive of each other's journeys.
Olivia's husband announced the news
They've also been public about their support for one another, with Kylie even giving Olivia a shout-out on her 70th birthday, writing: "Happiest of birthdays to the one and only ONJ."
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