Hong Kong–Taiwan relations
Relations between the government of Hong Kong SAR of the People's Republic of China (PRC) and the Taiwan Area of the Republic of China (ROC) encompass both when Hong Kong was under British rule or when the Republic of China controlled mainland China and afterwards the ROC fled to Taiwan. This is also a part of the Cross-strait relations.
Source: Wikipedia — Hong Kong–Taiwan relations (CC BY-SA 4.0)