The Little Mermaid statue, one of the best-known attractions in Denmark's capital Copenhagen, has been spray-painted with a "Free Hong Kong" slogan.
The words were found daubed in red and white on the rock the mermaid sits on.
It is just the latest incident in a long history of vandalism suffered by the tourist site.
Since first being put up more than 100 years ago, she has been decapitated, covered in graffiti and banned from Facebook over nudity.
The mermaid overlooking the waters at the port of Copenhagen is particularly popular with Chinese tourists.
In 2010, the 175kg (385lb) bronze statue was part of Denmark's pavilion at the World Exhibition in Shanghai.
Hong Kong has been gripped by months of protests demanding more democracy and less control from Beijing.
Created in tribute to the Danish storyteller Hans Christian Andersen, the mermaid has overlooked the entrance of the Copenhagen harbour since 1913 and over time has become a world-famous icon of the city.
Yet she has not enjoyed a quiet life. In 1964, her head was hacked off for the first time, never to be found.
Since then, one arm and the (replaced) head again have suffered the same fate while an explosion once knocked her off her rock into the water.
She has also been frequently sprayed with paint and graffiti, been covered with a burqa and banned from Facebook for breaching nudity guidelines.
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