The world's oldest known Sumatran orangutan has been reported dead in an Australian zoo aged 62, leaving behind 54 descendants.

Puan, described as the "grand old lady" of Perth Zoo, was euthanized on Monday due to age-related complications.

She had been at the zoo since 1968, and was officially recognised by Guinness World Records as the oldest of her species in 2016.

A critically endangered species, Sumatran orangutans rarely reach age 50 in the wild, the zoo said.

Believed to have been born in a jungle in Sumatra, Indonesia, in 1956, Puan left an "incredible legacy" of 11 children and a total of 54 descendants across the US, Europe and elsewhere.

"Her genetics count for just under 10% of the global zoological population. She did so much for the colony at Perth Zoo and the survival of her species,’’ primate supervisor Holly Thompson said.

Some of Puan's descendants have been released back into the wild in Sumatra, the zoo said.

According to the World Wildlife Fund, there are only about 14,600 Sumatran orangutans.

Puan's chief zookeeper wrote an obituary published in The West Australian newspaper on Tuesday.

"Over the years Puan's eyelashes had greyed, her movement had slowed down and her mind had started to wander, but she remained the matriarch, the quiet, dignified lady she had always been," Martina Hart wrote.