Chow was appointed by the State Council following a nomination and suggestion put forward by Chief Executive John Lee, according to Xinhua News Agency on Wednesday.
The former deputy commissioner takes over from Siu, who first took charge of the force in 2021 and had his tenure extended by two years when he reached the retirement age in 2023.
Siu was among six mainland and Hong Kong officials recently sanctioned by the United States.
Chow takes over the reins of the force on Wednesday.
He joined in 1995 as an inspector and spent most of his career in criminal investigation and intelligence gathering.
He was assigned temporarily to Interpol in France between 2012 and 2013 as a criminal intelligence officer.
Chow, who had been a deputy regional commander of Kowloon West at one stage, was known for leading a police operation at the Polytechnic University during the 2019 protests.
He further rose through the ranks with a series of back-to-back promotions since 2020 and assumed the No 2 position in the force by 2023.
As deputy police chief, his public appearances included hosting press conferences relating to test runs for the Kai Tak Sports Park.
For his part, Siu rose to the top post in June 2021, during which two pieces of national security legislation were enacted in Hong Kong.
He ends his decades-long career with the force by taking his leave on Wednesday.
