Crowds of protesters have begun demonstrating in what could be described as Hong Kong’s largest pro-democracy rally in more than a decade.
Organisers say the annual rally, which marks the day Hong Kong was returned to China in 1997, will focus on pressuring Beijing for full electoral freedom.
It comes days after an unofficial referendum on how to choose the chief executive drew close to 800,000 votes.
The Hong Kong government said the 10-day poll had no legal standing.
Several campaign groups have also indicated that they will stage peaceful overnight vigils after the march.
In 2003, the rally drew half a million people, who demonstrated against proposed anti-subversion laws which were later scrapped.