They came from across the city, carrying different banners and with a wide range of concerns. About the only thing that united them was a wish to see Chief Executive Leung Chun-ying ousted, just six months into the job.
For some, the reasons for marching were deeply personal. For others, the march was about wider concerns and the future direction of Hong Kong.
One 70-year-old who identified herself as "Sister Fong" said she was marching for the benefit of the next generation.
Fong, who lives with her daughter, said she felt Leung was not doing anything to improve elderly welfare, despite his claims to be putting livelihood issues first.
"I lost a tooth but I didn't have money to get an implant. If the government would give us HK$3,000 a month, I would be happy," she said as she joined other supporters of the Alliance for Universal Pensions. Her daughter earns about HK$10,000 a month but Fong said she did not want to rely on her.
"Everything is getting more expensive nowadays," she said. "She can barely make ends meet for herself."
For about 100 villagers from Fanling North, Kwu Tung North, Ta Kwu Ling and Ping Che, the issue was plans for massive new towns in the northeastern New Territories that would see their rural homes razed to make way for high-rise housing.
A Mr Leung, 40, said he had lived in Ma Shi Po village since childhood. He makes a living by farming and does not want to move into a flat.
"There will be much less space, and conflicts might arise," he said, adding that he only learned of the plan a year ago and that the government had not given villagers enough time to express their views.
Gay-rights groups marched under a rainbow banner, calling for anti-discrimination laws to protect homosexuals.
Salesman Aniel So, 18, said they had already waited for too long for laws to protect their rights. "We are now only asking the most basic right, laws to protect us from discrimination," he said.
National education was on the mind of May Chan, a 36-year-old housewife, who urged the government not to bring back the subject, which was shelved last year after massive protests and accusations that it represented "brainwashing".
"I need it to say clearly that it will not push forward the curriculum again," said Chan, who marched with her six-year-old son. "If it does not promise, it will introduce the curriculum again some time later."
Queenie Chow, 46, said she was unhappy about how the government had dealt with a dispute over the funding of the troubled Digital Broadcasting Corporation. "The government didn't help at all. That's a sign that freedom of speech is shrinking," she said.
Two groups marched under the colonial Hong Kong flag. Form Two student James Lau joined the anti-mainland group "We are Hongkongers, not Chinese", and said he hoped Hong Kong could return to its former glory, free of interference from Beijing.
He decided to protest with the British Hong Kong flag because he saw it as a reminder of better times. "Hong Kong local culture has been eroded and destroyed by the mainland," he said. "This needs to change. The number of mainland people coming down needs to stop."
The Hong Kong Autonomy Movement, another anti-mainland group, raised the colonial flag in Lee Garden Road, Causeway Bay.
Spokesman Vincent Lau said it was calling on four top government officials - Leung, Chief Secretary Carrie Lam Cheng Yuet-ngor, development chief Paul Chan Mo-po and education minister Eddie Ng Hak-kim - to resign for poor performances.