Marcus, 60, is a former deputy governor of the bank and former deputy finance minister as well as ex-chairwoman of Absa, South Africa's biggest retail bank.
She replaces Tito Mboweni, the country's first black Reserve Bank governor, whose prudent monetary policies over the past decade are credited with having helped stabilize the economy and attract and retain foreign investment during the first years of democracy.
An activist during apartheid with the African National Congress (ANC) in exile, Marcus was a popular choice for the job.
Like Mboweni, the doughty Marcus is expected to come under pressure from leftists within the ANC and its Communist and trade union allies to take a more flexible approach to inflation.
The bank has kept interest rates high in an attempt to keep inflation within a 3-6 per cent band. Mboweni's critics said the high interest rates were punishing the poor.
Marcus is one of a handful of women central bank governors in Africa. Among the others are Bank of Botswana governor Linah Mohohlo and Jacinta Mwatela, acting governor of Kenya's Central Bank.
Sapa-dpa
Steuart has done some 500 talks on South Africa's progress since 1994 and SA's prospects for the future' 
