Jacqueline Dark, an Australian opera and musical theatre singer, has died, aged 55.

Dark died in a Sydney hospital on Tuesday night, ABC reports.

The award-winning singer was diagnosed with a rare form of cancer and had undergone surgery and chemotherapy.

Australian tenor Kanen Breen, with whom Dark shared a son, Xander, wrote on Facebook the boy was the “love of her life”.

 “From the moment he existed, she did it all for him,” Breen said.

He detailed how she had pulled off a “Lazarus act” on Tuesday morning to fight the cancer one last time and spend a few more treasured moments with her son.

Jacqueline Dark, played Marianna, with David Lewis as Brushino Figlio and John Antoniou as Filberto in Rossini's Il Signor Brushino at Sydney's Opera House. Photo / Getty Images

“It [her heart] was standing next to her, in the shape of our boy, and we literally watched as she gave the last of her life to make him happy one last time,” he said.

“She took her last heroic breaths surrounded by profound peace and profound love.”

The esteemed opera singer was born in Ballarat, Victoria, and worked for 10 years as a maths and physics teacher before pursuing her dream, according to the Australian.

She performed opera across Australia and across the globe, winning various prestigious awards along the way.

She became more of a household name after appearing on So You Think You Can Dance and featuring as a guest panellist on the music quiz show Spicks and Specks.

Dark’s agent Patrick Togher reflected on the powerful legacy in Australian music that she had left.

“Jacqui’s magnificent voice and magnetic stage presence entrenched her place in Australia’s musical history; her indefatigably upbeat personality will be long remembered.”