The City Nature Challenge (CNC) is a large citizen science event covering cities around the globe. It was first held in 2016 by the California Academy of Sciences and Natural History Museum of Los Angeles County. CNC brings cities from around the world together. Citizens of participating cities record and identify local wildlife with the free app iNaturalist. Data collected during the competition would contribute to the global biodiversity database and assist scientists in ecological research.

Since 2023, OWLHK has been the volunteer city organizer for the City Nature Challenge (Hong Kong Region), helping to promote the City Nature Challenge in Hong Kong. Hong Kong region has achieved brilliant results over the past years. In 2026, 1,178 dedicated citizen scientists submitted 40,261 observations, including 4,126 species. In particular, 49.08% of observations reached "Research Grade", implying that the related data collected were of high quality.

For more updates about the Challenge, please refer to the website: https://www.owlhk.org/en/place-based-education/0600013/City+Nature+Challenge