People attend an anti-government demonstration organized by the opposition in Warsaw on June 4, 2023. AFP
Lech Walesa, a former Polish president, Nobel Peace Prize winner and leader of the fight against communism, joined opposition figures at the head of the march ahead of legislative elections in the autumn.
People travelled from across the country after former prime minister Donald Tusk, head of the centrist opposition party Civic Platform (PO), called for the protest against "the high cost of living, swindling and lying, and for democracy, free elections and the EU".
The leaders of most opposition parties encouraged their supporters to join the march against the nationalist Law and Justice party (PiS) led by Jaroslaw Kaczynski.
"City Hall estimates (the number of protesters) at 500,000 now," the organisers' spokesman Jan Grabiec told AFP.
Decked out in the red and white colours of the nation, demonstrators carried placards proclaiming "Enough's enough", "No to authoritarian Poland" and blaming the ruling PiS party for exorbitant prices.
Once the head of the European Council, Tusk addressed the crowds saying the opposition's role is "of comparable importance" to that in the 1980s and the fight against communism.
Walesa, who led the Solidarity union in a successful battle against communism, has long been absent from politics.
He told the marchers he had been "patiently" waiting for the day when the nationalist party and Kaczynski will be forced out.
"Mr. Kaczynski, we have come to get you. The day has finally arrived," Walesa said.
The June 4 protest march day is the 34th anniversary of the first partly free elections held in Poland which were followed by the defeat of communism in Europe.
Walesa became the nation's first democratically elected president in 1990.