South Africans are voting in presidential and parliamentary elections today, in what is being seen as a pivotal election after years of corruption scandals that have plagued the "rainbow nation".

Some 26.8 million voters are registered to cast ballots at 22,925 polling stations, and polls opened at 7am and will close 14 hours later today.

Early results will emerge on Thursday, while the official winner will be declared on Saturday.

The party that wins most seats in parliament selects the president who will be sworn in on May 25.

Wednesday's vote comes 25 years after the end of apartheid, but despite the demise of the system of racial discrimination, the country remains divided by economic inequality.

While dozens of parties are competing, the main contenders are the ruling African National Congress (ANC), Economic Freedom Fighters (EFF) and the Democratic Alliance (DA).