South Africa's rand plunged more than 5% overnight after President Jacob Zuma sacked Finance Minister Pravin Gordhan.
Nine other ministers were sacked as the president overhauled his cabinet.
Mr Gordhan was seen by many as a bulwark against corruption in an administration that is facing growing criticism.
President Jacob Zuma said in a statement that his midnight cabinet reshuffle was about a "radical socio-economic transformation".
Malusi Gigaba, previously the Minister of Home Affairs, has replaced Mr Gordhan
Sfiso Buthelezi will become Deputy Finance Minister, replacing Mcebisi Jonas.
President Zuma also made a number of other changes in the cabinet.
"I have directed the new ministers and deputy ministers to work tirelessly with their colleagues... to ensure that the promise of a better life for the poor and the working class becomes a reality," President Zuma's statement said.
Earlier this week, President Zuma recalled Mr Gordhan from planned
Last October, Mr Gordhan was charged with fraud - but the charges were later dropped.
He has described the allegations as politically motivated.
Mr Gordhan had been seen as standing up to President Zuma in cabinet and has warned against corruption becoming rampant.
The South African Communist Party, an ally of the governing African National Congress, had earlier lodged a formal objection to plans to dismiss Mr Gordhan, who is widely respected internationally.
Many senior ANC figures also opposed the finance minister's removal.
Meanwhile, the Democratic Alliance, South Africa's main opposition party, said it would call a vote of no-confidence in President Zuma in parliament.
Pressure has been growing on Mr Zuma to step down amid numerous allegations of corruption.
He denies the claims.