Singer and actress Olivia Newton-John, who gained acclaim in the film Grease, has died at age 73, 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," Mr Easterling said.
"Her healing inspiration and pioneering experience with plant medicine continues with the Olivia Newton-John Foundation Fund, dedicated to researching plant medicine and cancer."
He said Newton-John died peacefully at her home in Southern California surrounded by family and friends.
Newton-John, a four-time Grammy winner, had disclosed in 2017 that a recurrence of breast cancer had metastasized and spread to her lower back, forcing her to cancel performances. Twenty-five years earlier Newton-John had undergone a partial mastectomy, leading her to become an advocate for breast cancer research and other health issues and to establish a cancer treatment-research facility in Australia.
Newton-John was best-known for starring as girl-next door Sandy in the 1978 musical Grease alongside John Travolta, who played Danny.
Grease remained the highest-grossing musical for three decades, and Newton-John and Travolta had a close relationship long after the film hit cinemas.
With songs such as You're the One that I Want, Hopelessly Devoted to you and Summer Nights, the film's soundtrack is still one of the best-selling albums of all time.
Travolta paid tribute to his late co-star in an Instagram post.
"My dearest Olivia, you made all of our lives so much better. Your impact was incredible. I love you so much," he wrote.
"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 entertainer, whose career spanned more than five decades, devoted much of her time and celebrity to charities after first having breast cancer diagnosed in 1992.
The entertainer began performing as a child and became a global superstar after moving to the US. She was blond, blue-eyed and brimming with wholesomeness when she had her first hit in 1971 with If Not for You — a Bob Dylan song.
It would be followed in the next few years by Let Me Be There, which won her a Grammy for best female country vocal performance, and two No. 1 songs, Have You Never Been Mellow and I Honestly Love You.
The latter song won Grammys for best female pop performance and record of the year.
Newton-John also clinched the Country Music Association's female singer of the year title in 1974, edging out such homegrown American stars as Loretta Lynn and Dolly Parton.
The British-born and Australian-raised star dedicated numerous albums and performances to raise funds for research into early detection.
She performed into her late 60s, until the latest diagnosis.
Newton-John's family requested that, instead of flowers, donations be made to the Olivia Newton-John Foundation.
Agencies contributed to this report