South African President Thabo Mbeki has appointed Minerals and Energy Minister Phumzile Mlambo-Ngcuka as his deputy.
The announcement takes Ms Mlambo-Ngcuka into the highest political office held by a woman in South Africa.
She succeeds Jacob Zuma, who was sacked as deputy president last week after his financial adviser, Schabir Shaik was convicted of corruption and fraud.
Prosecutors later announced that Mr Zuma would face corruption charges next week. He denies wrong-doing.
Announcing Ms Mlambo-Ngcuka's appointment, Mr Mbeki said: "We thought that this gave us an opportunity further to strengthen the participation of women in the executive."
Since her appointment as minister of minerals and energy in 1999, Ms Mlambo-Ngcuka, 49, has won praise as one of the most effective ministers in the South African government.
President Thabo Mbeki is due to step down in 2009
Analysts say, however, that her appointment could prove controversial.
Her husband, former chief prosecutor Bulelani Ngcuka, initiated the investigation that led ultimately to the downfall of Ms Mlambo-Ngcuka's predecessor, Mr Zuma.
Mr Zuma angrily accused Mr Ngcuka of trying to ruin his reputation by leaking stories to the media.
Business and unions have welcomed the appointment.
Congress of South African Trade Unions spokesman said Ms Mlambo-Ngcuka "has a soft spot for workers and has done everything to take them on board in the difficult process of transforming the minerals and energy industry".
Business Unity South Africa chief executive Bheki Sibiya said: "We welcome with excitement the appointment of Mrs Mlambo-Ngcuka."
The state oil company, Sasol, welcomed a "thoroughly well deserved" appointment.
Tony Leon, leader of the opposition Democratic Alliance, described the appointment as "bold and gender-friendly move".
But he expressed concern over unanswered questions surrounding a recent scandal over state oil purchases, as well as Mr Ngcuka's role in the Zuma case.
The departure of Mr Zuma, previously seen as heir apparent to the presidency, has opened the race to succeed Mr Mbeki when he steps down in 2009.
He has said that he would like his successor to be a woman.
The BBC's Justin Pearce in Johannesburg says though that Ms Mlambo-Ngcuka cannot automatically be assumed to be Mr Mbeki's successor.
Mr Mbeki also announced the appointment of Lindiwe Hendricks, formerly deputy minister of trade and industry, to replace Ms Mlambo-Ngcuka as minister of minerals and energy.