Australia Zoo staff are in mourning after the country's oldest elephant passed away overnight.

Staff and volunteers were extremely upset on Tuesday after learning of Siam's sad death.

Siam, who was reportedly grazing at the back of the zoo with fellow elephants, died of kidney failure at the tender age of 58.

The much loved animal spent the last decade of her life in Beerwah and was found in the early hours of Tuesday morning, according to News Limited reports.

Zookeepers were keeping a close on the mammal, aware that age was beginning to weary her. However they were not conscious of any kidney-related illness.

"As the largest of our three Asian elephants, she was affectionate, cheeky and endearing," the zoo said.

"She will be sorely missed."