Anger over corruption, the faltering economy and land reform are key issues as South Africans vote in the sixth democratic nationwide election since apartheid ended 25 years ago.
The African National Congress (ANC), which led the fight against apartheid, has governed the country since 1994.
But its support has eroded as large inequalities have remained.
The centrist Democratic Alliance (DA) and left-wing Economic Freedom Fighters (EFF) are providing the main challenge.
Apartheid, in place from 1948 to 1994, legalised racial discrimination privileging white people, and land ownership has remained a contentious issue.
The white minority still owns disproportionately more land than the black majority. The EFF has led the charge in trying to change this.
The BBC’s Andrew Harding in Johannesburg says the party’s stance has forced the ANC to consider drastic measures to transfer more land, more quickly, into black hands, which has resulted in a pledge to conduct land expropriation without compensation.
Meanwhile the main opposition party, the DA, says it does not believe land reform needs to be “carried out in a way that takes from one to give to another”, and instead promises to prioritise land reform in the budget and to release unused government land.
Other election issues include discontent over poor basic services such as water, housing and electricity and anger over violent crime.