The turnout for the rally could show whether the movement still has broad-based support after the ugly scenes witnessed during the past week when protesters occupied the city's airport, for which some activists apologised.
Anger over a now-suspended bill that would allow criminal suspects in Hong Kong to be extradited to mainland China erupted in June, but the rising unrest is fuelled by broader worries about the erosion of freedoms guaranteed under the "one country, two systems" formula put in place after Hong Kong's return from British to Chinese rule in 1997.
"Hong Kongers are tired of protesting, this is really the last thing they want. It's bloody hot and it's raining. It's a torture just to turn up, frankly," said a 24-year-old student named Jonathan.
"But we have to be here because we have no other choice. We have to continue until the government finally shows us the respect that we deserve," he said.
Seated on concrete soccer fields in the sprawling Victoria Park in the city's bustling Causeway Bay district, protesters held placards with slogans including "Free Hong Kong!" and "Democracy now!", and umbrellas to shield them from the heavy rain.
Demonstrators are seeking complete withdrawal of the extradition bill, a halt to descriptions of the protests as 'rioting', a waiver of charges against those arrested, an independent inquiry and resumption of political reform.
They have also called for the resignation Hong Kong's Beijing-backed leader, Carrie Lam.
"When we were young, we didn’t think about it. But my son tells me: After 2047, what will happen to me?," said a history teacher named Mrs. Poon, referring to the year when the 50-year agreement enshrining Hong Kong's separate system will lapse.
"I will come again and again and again. We do not know how any of this is going to end. We will still fight," she said.
Police have come under criticism for using increasingly aggressive tactics to break up demonstrations, and on Sunday some people handed out balloons resembling eyeballs, a reference to the injury suffered by a female medic who was hospitalised after being hit by a pellet round in the eye.
On Saturday, however, a demonstration in support of the government attracted what organisers said was 476,000 people, although police put the number of attendees at 108,000.
The anti-government protests present one of the biggest challenges facing Chinese President Xi Jinping since he came to power in 2012. And with the ruling Communist Party preparing to mark the 70th anniversary of the founding of the People's Republic on 1 October, the crisis in Hong Kong has come at a sensitive time.
Beijing has struck an increasingly strident tone over the protests, accusing foreign countries including the United States of fomenting unrest.
Scenes of Chinese paramilitary troops training at a stadium in the city of Shenzhen, which borders Hong Kong, gave a clear warning that mainland intervention by force is possible.
Last week, protesters who occupied the terminal at Hong Kong's airport forced the cancellation of nearly 1,000 flights and detained two men they thought were pro-government sympathisers, prompting Beijing to liken the behaviour to terrorism.
"We are Hong Kongers. We are here for our future. We feel for the teenagers," said Frances Chan, 60, a retired journalist attending Sunday's rally.
She said only a few protesters had used violence, sparingly, and that it was brought on by pressure from authorities and police.
"Actually, we want peace and freedom," she said. "If the government would just listen to the five requests, things would calm down."