The British-born 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 is also a multi-platinum selling singer, with two singles and two albums having earned the stamp 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, held in Brighton, 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.

"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."

Mr Easterling added that in lieu of flowers, donations be made to Newton-John's foundation.

She is survived by her husband as well as her daughter Chloe Lattanzi.

Olivia Newton-John's life had more than its share of wonderful highs, but lurking not too far behind she also experienced some terrible lows.

Newton-John battled and defeated breast cancer in 1992 before its reappearance in 2013, and the British-born Australian has died at her ranch in Southern California on Monday aged 73.

Newton-John was born on September 26, 1948, in Cambridge, England, where her father Bryn had been working on the Enigma project at Bletchley Park during WWII.

When she was six years old her family emigrated to Melbourne, where she attended Christ Church Grammar School and University High School.

After winning a trip to the UK on a TV talent show, Newton-John decided to try her luck in Great Britain where she recorded and released her first single for Decca in 1966.

International success eluded her until her first solo album in 1971, when the singles If Not For You and Banks of the Ohio charted around the world.

That began a string of hits including Let Me Be There, her signature tune I Honestly Love You, and 1981's Physical which topped the US charts for 10 consecutive weeks.

During her life Newton-John received four Grammy Awards, an Emmy Award, numerous Country Music Awards, American Music Awards and People's Choice Awards.

Her acting career took off in 1978, when the world fell in love with her as the sweet Sandy Olsson in the movie musical Grease alongside John Travolta, and two years later she danced with screen legend Gene Kelly in Xanadu.

The singer kept her head high through the mysterious disappearance of her boyfriend of nine years, Patrick McDermott, who was thought to have drowned off the coast of California in 2005 until evidence emerged in 2009 suggesting he had faked his death and was hiding in Mexico.

Despite the tough breaks in her personal life, Newton-John always bounced back, turning tragedy into a positive force with charities and movements ranging from cancer research to the environment.

In 1991, Newton-John turned tragedy into a cause that would help others when her daughter, Chloe, lost her best friend, Colette Chuda, to cancer.

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Newton-John helped form the Colette Chuda Environmental Fund in the United States, assisted with the foundation of Australia's Planet Ark organisation in 1993 and served as Goodwill Ambassador to the United Nations Environment Programme.

She also actively supported Melbourne's Austin Hospital in building the Olivia Newton-John Cancer Wellness and Research Centre, and promoted the LIV-KIT device for breast cancer detection.

She received many honours including being appointed an Officer in the Order of Australia (OA) in 2006.

That followed an Order of the British Empire (OBE) honour bestowed upon her by Queen Elizabeth II in 1979.

In 2012 the National Trust of Australia named her a National Living Treasure.

One of Newton-John's latest awards came in 2006 at the G'day LA Ball in Hollywood, where she was presented with a Lifetime Achievement Award by Travolta.

Travolta said he admired how Newton-John had survived the ups and downs in her life.

"We've been friends for 28 or 29 years and we have always been there for each other no matter what, thick or thin," Travolta said.

In May 2017 the singer announced she was cancelling a tour due to the recurrence of her breast cancer, which had metastasised to her back and would be undergoing treatment at the cancer centre named after herself in Melbourne.

Newton-John married twice, first in 1984 to actor Matt Latanzi after they met on the set of Xanadu.

The couple divorced in 1995 and in 2008 Newton-John secretly wed John Easterling, the founder of natural remedy firm Amazon Herb Company.

She is survived by her daughter, singer and actress Chloe Rose Lattanzi.

John Travolta paid tribute to his "dearest" writing on Instagram: "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! Your Danny, your John!"

American singer and actress Barba Streisand wrote on Instagram "too young to leave this world. May she RIP".

Actor George Takei wrote on Twitter "I trust she is now in the great Xanadu beyond. Know that we are forever hopelessly devoted to you, Olivia. Rest in song and mirth."

Richard Marx tweeted: "My heart is broken. Rest now, sweet friend. You were as kind and loving a person as there's ever been. I'll miss you every day."

Australian Associated Press