Olivia Newton-John Of 'Grease' Has Died & John Travolta Posted A Touching 'Danny' Tribute

Fans of Grease and many others, including John Travolta, are mourning the death of Olivia Newton-John, the Australian actress and singer who just died of cancer at the age of 73.

Newton-John died Monday morning at her California ranch while "surrounded by family and friends," according to a statement posted on her official Instagram account by husband John Easterling. She had been on a "journey with breast cancer" for over 30 years, according to the statement.

Newton-John started her career as a singer in the 1970s and then broke into acting as Sandy in the film version of Grease, opposite John Travolta as Danny. She went on to split the rest of her career between music and acting.

"My dearest Olivia, you made all of our lives so much better," Travolta wrote in a tribute post on Instagram.

"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!"

Stockard Channing, who played Rizzo in the film, also mourned her former co-star.

"I don't know if I've known a lovelier human being," Channing told People in a statement.

"Olivia was the essence of summer — her sunniness, her warmth and her grace are what always come to mind when I think of her.

"I will miss her enormously."

Fans also paid tribute to the actress by sharing photos and clips of her online.

One clip of Newton-John and Travolta singing You're The One That I Want in Grease racked up 1.3 million views on Twitter in less than a day, as fans remembered and marvelled at her performance.

"I grew up listening to her music and desperately wanted to look just like her," said one of the top commenters on the video.

"Grovelling in front of a woman smoking a cigarette is something we lost as a society," added another.