The British-born and Melbourne-raised singer died peacefully at her ranch in southern California on Monday morning, surrounded by family and friends.
Newton-John is best known for her starring role in the 1978 film Grease, in which she starred opposite John Travolta as Sandy.
Her performance saw her nominated for multiple awards including two Golden Globes, and various other film accolades.
She was honoured with the star on the Hollywood Walk of Fame almost 41 years ago to the day of her death, on August 5, 1981.
Writing on Instagram, Travolta said her "impact was incredible" and signed off his tribute as "your Danny".
"My dearest Olivia, you made all of our lives so much better," he wrote.
"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! Your Danny, your John!"
The soundtrack to Grease is one of the world's best-selling albums of recorded music and features the two hit duets from Newton-John and Travolta: Summer Nights and You're The One That I Want.
The latter also ranks as one of the best-selling singles ever.
Aside from her hit role in the film, Newton-John was also a multi-platinum selling artist, with two singles and two albums having earned the certification from the Recording Industry Association of America.
Newton-John also represented the UK in the 1974 Eurovision Song Contest with the song Long Live Love.
She finished fourth in the competition losing out to ABBA, with their hit song Waterloo.
In a statement posted to Instagram, her husband John Easterling wrote: "We ask that everyone please respect the family's privacy during this very difficult time."
Aside from her showbusiness career, Newton-John became a prominent breast cancer campaigner after being given the first of three cancer diagnoses in 1992.
Following her initial battle with the disease, she had a partial mastectomy and reconstruction.
She remained cancer-free until a recurrence in 2013, but revealed she had been diagnosed with cancer for the third time in three decades in September 2018.
At the time, she told Australian news program Sunday Night that doctors had found a tumour in her lower in 2017.
The singer said she was treating the illness "naturally" and was using cannabis oil made from marijuana her husband grows in California to alleviate the pain.
"Olivia has been a symbol of triumphs and hope for over 30 years sharing her journey with breast cancer," Easterling said in his Instagram post.
"Her healing inspiration and pioneering experience with plant medicine continues with the Olivia Newton-John Foundation Fund, dedicated to researching plant medicine and cancer."
Easterling said that in lieu of flowers, donations be made to Newton-John's foundation.
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