Last month the electoral commission barred him over a contempt of court conviction.

It argued the constitution prevented people from holding public office if convicted of a crime and sentenced to more than 12 months in prison.

Mr Zuma, 81, has been campaigning for the new uMkhonto we Sizwe (MK) party.

A former stalwart of the governing African National Congress (ANC), he is a controversial figure and served as president from 2009 until 2018, when he had to step down because of corruption allegations.

He was sentenced to 15 months in jail in 2021 for failing to testify in a corruption investigation, though he only served three months on health grounds.

The ruling could have a significant impact on the outcome of next month's election.

Mr Zuma is the face of a newly formed MK opposition party, which is named after the ANC's former military wing.

The ex-president sees himself as the true heir to the revolutionary roots of ANC, once led by Nelson Mandela.

Mr Zuma's court victory means he can now run as the MK's leading candidate.

Rather than voting directly for a president, South Africans elect members of the National Assembly. The head of whichever party can muster a majority is likely to become the country's leader, though it could put forward another candidate.

The ruling will also be a blow to the ANC, which after 30 years in power, faces a potentially bruising election.

For the first time since the start of the democratic era in 1994, the ANC's vote share could fall below 50%, several opinion polls predict.