Heidi, the famous cross-eyed opossum, has been put to sleep at Leipzig zoo, Germany's N-TV channel said on Wednesday.
Heidi, who had thousands of Facebook and Twitter admirers, was being treated for arthritis and other symptoms of old age during the past weeks but the marsupial's condition was getting worse.
The opossum, who was three-and-a-half years old, was cross-eyed because she was overweight, leading to fatty deposits behind her eyes. But experts said that this defect caused the animal no problems.
Heidi first attracted attention at the end of 2010 after she appeared on a local television report and became another animal star in Germany, where polar bear Knut and Paul the octopus have also achieved fame.