Hong Kong, ex-colony of Great Britain, is a Special Administrative Region of the People’s Republic of China, its high degree of autonomy from Beijing being sanctioned by the policy ‘One country, two systems’. Its peculiar language situation consists in the formal coexistence of three official languages under the ‘Biliteracy and Trilingualism’ policy: Cantonese, first language of the majority of the population, English, with its international value, and Putonghua, symbolizing Hong Kong’s tight relations with mainland China not only from a political, but also from an economic point of view. The present work focuses on the evolving relationship between Cantonese and Putonghua in the territory, with the goal of delivering a sociolinguistic overview of their situation and investigating on the perspectives of their equal, harmonious coexistence in future Hong Kong. This work thus gives a linguistic introduction to spoken and written Cantonese and compares it with Putonghua by means of contrastive analysis, evaluating the degree to which it can be considered a standard language. It then goes through the complex history of Hong Kong, tracing the evolution of its language situation. It describes Hong Kong’s language policies and the way they shaped the status of Cantonese and Putonghua in the local education system, finally introducing issues of local identity and language attitudes in Putonghua learning. The work concludes that, instead of a potential threat for the very existence of Cantonese on the local stage, Putonghua could become a source of stability. To make this possible, some measures are proposed, such as: standardization of Cantonese language and allocation of more resources for guaranteeing its longevity; enhancement of Cantonese learning in schools and harmonization of Putonghua learning promotion; planning of politically neutral, balanced language policies to ensure the successful achievement of the ambitious goal of ‘Biliteracy and Trilingualism’.