Singer and actress Olivia Newton-John died on Monday at age 73 after a long battle with cancer. Since her breakout role as Sandy in the musical movie “Grease,” Newton-John has touched the lives of countless fans and co-stars, and many paid tribute to the star on social media this week.

John Travolta, who starred alongside Newton-John in “Grease,” posted a touching message on Instagram, sharing an old photograph of the star. “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!”

Travolta ended the post with, “Your Danny, your John!” referring to his role as Danny Zucco opposite Newton-John’s Sandy in “Grease.”

Oprah remembered a “spontaneous” dinner she had with Newton-John and “CBS Mornings” co-host Gayle King, after King interviewed Newton-John in 2019. “Her positivity was just infectious,” Oprah tweeted, sharing a photo from the night.

Mariah Carey posted about her long-time admiration of Newton-John. “I first fell in love with Olivia’s voice when I was a little girl and heard ‘I Honestly Love You.’ Songs like ‘Magic,’ ‘Suddenly’ and ‘Have You Never Been Mellow’ showcased her beautiful airy tone and signature sound. And THEN there was GREASE. I was obsessed,” she wrote.

Years later, Carey said, she got to sing with Newton-John at a concert in Melbourne, Australia, where Newton-John grew up. “This is a moment I will never ever forget,” Carey wrote. “I was also blessed to be in her presence on many other occasions and she was one of the kindest, most generous and lovely people I’ve ever met. She will be missed. She will be remembered. She will be loved. Olivia, I honestly love you”

Another iconic singer, Dionne Warwick, called Newton-John a dear friend. “Another angelic voice has been added to the Heavenly Choir,” she tweeted. “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.”

Singer Rod Stewart remembered Newton-John as “the perfect Lady, gorgeous, with great poise and with a certain Aussie sophistication.”

“Her spandex trousers in Grease were my inspiration for my ‘Da ya think I’m Sexy’ era,” he tweeted.

Julianne Hough, who followed in Newton-John’s footsteps and played Sandy in “Grease Live” in 2016, shared a video of herself singing “Hopelessly Devoted to You” during the production.

TV host and producer Andy Cohen shared a video of Newton-John singing the hit song from “Grease,” writing: “Hopelessly Devoted to YOU, Olivia Newton John. Rest In Peace, Queen. Thank you for the music.”

“Oh man!!! You were my childhood!!” actress Viola Davis tweeted. “Your talent, poise, beauty!! Rest in glorious peace. God bless your family….and thank you for creating eternal memories.”

Fellow Australian singer Kylie Minogue said she had looked up to Newton-John since she was 10 years old. “And, I always will,” she tweeted. “She was, and always will be, an inspiration to me in so many, many ways. My deepest condolences to her family and loved ones.”

Australian Prime Minister Anthony Albanese also remembered the star on Twitter. “Olivia Newton-John was a star. A bright, joyful glow in our lives,” he wrote. “From the moment we saw her, she was a warm, enduring presence and her voice became a big part of the Australian soundtrack. Above all she was a wonderful, generous person.”

Some monuments and buildings across Australia were lit up in pink to honor the star. Optus Stadium and Matagarup Bridge in Perth, Western Australia, were lit up, according to WA Premier Mark McGowan.

Other buildings, like the Melbourne Cricket Ground, were also lit up, and several Twitter users in Australia shared images of the pink monuments.

Dan Andrews, premier of Victoria, said while Newton-John “gave the world her music and movies – but for Victorians she was so much more.”

“Her generosity through the ONJ [Olivia Newton-John] Cancer Wellness and Research Centre has saved lives, and her advocacy has given Victorians hope as they battle cancer,” he wrote.

The center is a researcher and treatment facility in Victoria. Newton-John was first diagnosed with cancer in 1992 – her diagnosis came the same weekend her father died of cancer. She underwent a partial mastectomy, chemotherapy and breast reconstruction to treat it, and battled cancer several more times.

The ONJ Centre said the star’s dream “was supporting people with cancer person through supportive wellness therapies.”

“She found them so helpful to her journey that she wanted everyone to have access to them,” they wrote on Tuesday. “Olivia was a driving force to win over cancer, for treating the whole person and looking after their mind, spirit and body. Having the opportunity to meet Olivia was a joy, her kindness and light was irrepressible.”

The center is planning a memorial so staff, patients and their families can pay their respects to Newton-John.