The Australian entertainer died peacefully at her ranch in southern California on Monday morning at the age of 73, with her husband confirming her death on social media.

She is best known for her starring role as Sandy in the 1978 film Grease, in which she appeared opposite Travolta, who played Danny Zuko.

Writing on Instagram, Travolta said her "impact was incredible" and signed off his tribute to the actress 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 worlds of television, film and music took to social media to share memories and send condolences to her family.

Dionne Warwick, who recorded a duet with Newton-John in 2006, tweeted: "Another angelic voice has been added to the Heavenly Choir.

"Not only was Olivia a dear friend, but one of the nicest people I had the pleasure of recording and performing with. I will most definitely miss her.

"She now Rests in the Arms of the Heavenly Father."

US singer Richard Marx, who also duetted with Dame Olivia, said he would "miss her every day".

"My heart is broken. Rest now, sweet friend," he wrote on Twitter.

"You were as kind and loving a person as there's ever been. I'll miss you every day."

Oscar-winning actress Marlee Matlin recalled starring alongside Dame Olivia in the 1996 film It's My Party, one of the first films to address the topic of Aids patients dying with dignity.

She said on Twitter: "I am SO saddened at the news of the passing of Olivia Newton John.

"I remember being so star struck when I met her at my first Hollywood gathering for Paramount.

"She was the sweetest and brightest light and I loved getting to know her on It's My Party. RIP dear, sweet Olivia."

British actor Sanjeev Bhaskar recalled the actress' kindness during a brief encounter many years prior.

"Ah so sad. I met Olivia Newton John once many years ago. In that 5 min chat I felt like I'd been blessed," he said.

"She didn't know me from a pumpkin but was so warm, interested and charming. I was hopelessly devoted to her all over again."

Singer Nancy Sinatra said although she had not known Newton-John personally, she had admired her for "the way she faced her health battles".

"Beautiful & strong, she fought to the end," she wrote.

American filmmaker and actor James Gunn called her his "first real crush" and revealed he previously bought her home in Malibu.

"Really sad to hear about the passing of Olivia Newton-John," he tweeted.

"My first real crush as a kid.

"I loved Grease & her music & I coincidentally also bought & lived in for a while the wonderful home she built in Malibu. May she Rest In Peace."

Filmmaker Edgar Wright, whose credits include Last Night in Soho and Baby Driver, added: "Olivia Newton John so completely dominated the charts and Top Of The Pops when I was a kid, it felt like she was pop music.

"And yes, Xanadu is still a stone cold classic song. RIP."

Kiss co-founder and frontman Paul Stanley said in a brief tribute: "So very sad. She was everyone's sweetheart."

Australian Associated Press