Jia Jia, the oldest giant panda in captivity, has been euthanised aged 38.
Hong Kong's Ocean Park said Jia Jia's health had rapidly deteriorated in the last few weeks and worsened on Sunday morning (local time).
The decision was made to euthanise her so as to not prolong her suffering, they said.
"Jia Jia was a member of their family who had spent 17 wonderful years with Hong Kong people, and she will be deeply missed," says Leo Kung Lin-cheng, Ocean Park's chairman.
"This is a day we knew would eventually come, but it is nevertheless a sad day for everyone at the park, especially for the park's keepers who took care of her over the years."
Giant panda Jia Jia looks on beside a birthday cake made from ice and vegetables as she celebrates her 37th birthday (Reuters / file)
Before her death, Jia Jia had been diagnosed with cataracts in both eyes, high blood pressure and arthritis.
Jia Jia's equivalent age in human years was around 114 years old.
She was gifted to the Hong Kong park in 1999 along with another panda, An An, from Beijing.
An An, now 30, remains at Ocean Park along with 11-year-old pandas Ying Ying and Le Le.
Pandas usually live to around 20 years old in the wild, or up to 30 in captivity, according to World Wildlife Fund.