Hong Kong, currently a Special Administrative Region of China, has never had its own anthem. As a colony of the United Kingdom from 1842 to 1997, it used the anthem of that country as its official anthem, and after control was given to China, the Chinese anthem has been used to represent Hong Kong.

While there is not (nor has been) a local anthem for the region, during the 2019-2020 protests against Chinese control a protest song “Glory to Hong Kong” by a pseudonymous author has gained widespread popularity in the region among protestors, and has been referred to as the “unofficial national anthem”[1] [2], it is currently used in context of the protests, rather than in a broader sense for all aspects of the region.

Sources:
[1] Hillary Leung, “Listen to the Song That Hong Kong’s Youthful Protesters Are Calling Their ‘National Anthem’,” Time, September 10, 2019, https://time.com/5672018/glory-to-hong-kong-protests-national-anthem/.
[2] Daniel Victor, “Hong Kong Protesters, Without an Anthem to Sing, Create One Online,” The New York Times, September 12, 2019, https://www.nytimes.com/2019/09/12/world/asia/glory-to-hong-kong-anthem.html.