Who currently rules Hong Kong?

As of my most recent update in September 2018, the Chief Executive of the Hong Kong Special Administrative Region of the People's Republic of China is Carrie Lam. She was elected on March 26, 2017, and is the fourth Chief Executive of Hong Kong since its establishment in 1997. It's possible that there have been updates to the position since then. For the most current information, I suggest checking the official government website of Hong Kong.