The weekly mass demonstrations -- among the largest seen in South Korea since the pro-democracy protests of the 1980s -- have provided a stark challenge to Park's authority, but the president has defied calls to step down.
After claiming a turnout of around one million for last Saturday's protest, organisers said they expected around 500,000 people to march in Seoul, with a similar number demonstrating in other cities across the country.
So far the candlelight protests have been largely peaceful, with many families participating, but there was still a heavy police presence on Saturday, with buses and trucks blocking access roads to the presidential Blue House.
"We want to have a peaceful protest as in the three previous rallies", Nam Jeong-Su, spokesman for the Korean Confederation of Trade Unions, told AFP.
Nam said he expected the ranks of protestors to be swelled by thousands of students who sat the national college entrance exam earlier in the week.
And this being South Korea -- with the world's highest smartphone penetration rate -- many had downloaded a special app showing a burning candle to hold aloft during the rally.
Protestors were expected to converge on Seoul's ceremonial Gwanghwamun boulevard at around 5:00pm (0900 GMT) to hear speeches before heading towards the Blue House and the police barricades.
