Crowds sang at the James Motlatsi stadium in Orkney, in the Free State, in celebration of the 30th anniversary of the National Union of Mineworkers (NUM).
The union was founded on December 4, 1982, in Klerksdorp, which is now known as Matlosana.
"The rally is going very well," said NUM spokesman Lesiba Seshoka.
He estimated that between 7 000 and 10 000 people were at the stadium.
"We've always been hoping to get around 10 000... We are within our expectations," he said.
Some were still entering the stadium, while others were singing.
NUM president Senzeni Zokwana, Congress of SA Trade Unions general secretary Zwelinzima Vavi, and SA Communist Party second deputy general secretary Solly Mapaila were expected to speak.
"NUM has throughout the years become the only voice of the voiceless mineworkers, construction and energy workers in the country," the union said in a statement.
"It is through its gallant fight that miners who have for many years of service taken only a helmet and a pair of boots on retirement have retirement benefits today."
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