Activists say the semi-autonomous city risks losing its rights and freedoms under growing pressure from Beijing.
Hundreds of people took to the streets of Hong Kong on Sunday to protest against what they perceive as China's authoritarian rule.
They were led by high-profile democracy campaigners including Joshua Wong, who was jailed in August over his role in the Umbrella Movement mass protests of 2014 and is currently on bail pending an appeal.
Wong, 21, vowed to “continue to fight in this long term battle."
Hong Kong was handed back to China by Britain in 1997 and is run by a "one country, two systems" deal that grants it a high degree of autonomy, with its own legal system and freedoms unseen in mainland China.
But protesters fear the semi-autonomous city is losing its special rights and freedoms in the face of growing pressure from Beijing.
Earlier this year, a court removed four pro-democracy legislators from office for having turned their oath-takings into apparent protests against China.