The legendary actress/singer passed away peacefully at her ranch in Southern California on Monday morning following a battle with cancer. She was 73.

Following the sad news, Stockard issued a statement to People in which she remembered her co-star in the 1978 film Grease.

"I don't know if I've known a lovelier human being. Olivia was the essence of summer - her sunniness, her warmth and her grace are what always come to mind when I think of her," she praised. "I will miss her enormously."

In addition, music star Elton expressed his condolences to Olivia's family and loved ones.

"The saddest of news to wake up to. Olivia was a beautiful and courageous woman, who I never heard complain about her illness. A beautiful voice and a warm and loving friend. I will miss her so much," he wrote on Instagram.

Elsewhere, a number of Australian celebrities took to social media to pay tribute to the Xanadu star.

Kylie Minogue posted on Instagram that Olivia will "always be an inspiration" while Hugh Jackman shared that he was "devastated" by the news, and described the singer as a "one of a kind spirit".

Nicole Kidman and Keith Urban also posted a joint statement in honour of their friend.

"Livvie brought the most divine light into the world... so much love, joy, inspiration and kindness... and we will always be hopelessly devoted to you," they commented.

Other stars to share tributes online include Rod Stewart, Kate Hudson, Pink, and Mariah Carey.

Olivia was first diagnosed with breast cancer in 1992, and while she recovered at the time, the disease returned in 2017.

She is survived by her 36-year-old daughter Chloe Lattanzi and husband John Easterling.