The star died at her home in Southern California surrounded by family and friends, her husband John Easterling said on Instagram.
“Olivia has been a symbol of triumphs and hope for over 30 years, sharing her journey with breast cancer,” he wrote.
Chopra Jonas took to Instagram, where she posted a photo of Newton-John as Sandy from the 1978 musical Grease, in which she played opposite John Travolta, writing: “Rest in peace, Olivia Newton-John. Your legacy will always shine on.”
Travolta was among the first to lead tributes to his co-star. He posted a throwback photo of Newton-John on Instagram, writing in the caption: “My dearest Olivia, you made all of our lives so much better. Your impact was incredible. I love you so much. We will see you down the road and we will all be together again. Yours from the first moment I saw you and forever!”
He signed off as “Your Danny, Your John”, referring to his character in Grease.
Fellow Australian celebrities flooded social media platforms, including Kylie Minogue, who posted a poignant tribute on Twitter.
“Since I was ten years old, I have loved and looked up to Olivia Newton John. And, I always will,” the singer, who has also battled breast cancer, wrote alongside a black-and-white photo of the two of them.
“She was, and always will be, an inspiration to me in so many, many ways. My deepest condolences to her family and loved ones.”
Australian actress Rebel Wilson, also paid tribute on Instagram, posting a more recent photo of her with the breast cancer awareness advocate.
“You were the most gorgeous lady inside and out, you are a true Aussie icon and to play your daughter on screen in A FEW BEST MEN was beyond an honour,” Wilson wrote.
“Seeing you star in the huge Hollywood blockbuster GREASE with your natural accent was so instrumental to me as a little girl, helping me to believe that it was possible for an Aussie girl to star in huge international musicals.”
Wilson said Newton-John taught her about health “years before I took it seriously”.
“What a complete legend you are! I am so sad you are gone,” she said.
Australian actor Hugh Jackman also shared his condolences on Instagram, alongside a throwback photo of the two together.
“I’m devastated to hear the news that @therealonj has passed away. One of the great privileges of my life was getting to know her. Not only was she one of the most talented people I’ve known … she was one of the most open hearted, generous and funny.
“She was a one of kind spirit. It’s no secret Olivia was my first crush. I kissed her [poster] every night before bed. Her legacy will only grow stronger in the years to come. A fighter for healing from cancer that knows no bounds.”
Fellow singer and actress Barbra Streisand also posted a tribute on Instagram, writing: “Too young to leave this world. May she RIP.”
Singer Rod Stewart honoured Newton-John, his “great friend”, on Twitter, again with a shot of her in Grease.
“She was the perfect Lady, gorgeous, with great poise and with a certain Aussie sophistication. Her spandex trousers in Grease were my inspiration for my Da ya think I’m Sexy era.”
Australian Prime Minister Anthony Albanese also paid tribute, alongside numerous other politicians in Newton-John's home country.
The newly elected official wrote a touching tribute, alongside a photo of the pair together.
“Olivia Newton-John was a star. A bright, joyful glow in our lives. From the moment we saw her, she was a warm, enduring presence and her voice became a big part of the Australian soundtrack. Above all she was a wonderful, generous person.”
Celebrities weren't the only ones mourning Newton-John, as fans flooded Hollywood's Walk of Fame on Tuesday, putting flowers on the Xanadu actress's star.
Scroll through the gallery below to see fans mourning Olivia Newton-John