"One of the nicest, sweetest, most graceful human beings has passed away" - Chris Evert on Hollywood icon Olivia Newton-John

Tennis legend Chris Evert was one of many across the world to express sadness at the passing of Hollywood icon Olivia Newton-John on Monday.

Evert shared a poignant and graceful post on Twitter while celebrating the achievements of Newton-John. She referred to the Grease star as "one of the nicest, sweetest and most graceful human beings."

"One of the nicest, sweetest, most graceful human beings has passed away. She shed a bright light wherever she went. She was so loved…RIP Olivia…," Evert wrote.

Olivia Newton-John was one of the most popular recording artists of the 70s and 80s, her biggest hit being "Physical," which spent 10 weeks at No. 1 on the US Billboard charts. She also starred in several of the most iconic movies, including Grease and Xanadu.

"I’ve lived a very charmed life, now I have some challenges ahead of me" - Chris Evert on her battle with cancer

Chris Evert acknowledges spectators at the Centre Court centenary celebration on Day 7 of the Wimbledon Championships

Chris Evert, an 18-time Grand Slam champion and one of the greatest players in tennis history, spoke earlier this year about her battle with cancer and her impending chemotherapy sessions.

She revealed that she was nervous as she headed into a phase of her life that she had no control over.

“In tennis, you can control a situation. This type of thing, you can’t control it. Thousands and thousands of people have cancer. I’m just like everybody else,” Evert said.

Evert said she'd lived a "very charmed life" but had some challenges ahead.

"I’ve lived a very charmed life. Now I have some challenges ahead of me. But I have comfort in knowing the chemotherapy is to ensure that cancer does not come back," she said.

"As someone who has always had control over my life, I have no idea how I'll respond to chemotherapy. I have to give in to something higher." she added.

In July, Evert graced Wimbledon's famed Centre Court during its centenary celebration. The American was joined by the likes of Rod Laver, Martina Navratilova, Venus Williams, Roger Federer and plenty of other legends in the sport.