The UK will end its aid programme in South Africa by 2015, said International Development Secretary Justine Greening.
The secretary will announce the move at a conference of African ministers and business leaders in London on Tuesday.
"South Africa has made enormous progress over the past two decades, to the extent that it is now the region's economic powerhouse and Britain's biggest trading partner in Africa," she will say.
"We are proud of the work the UK has done in partnership with the South African government, helping the country's transition from apartheid to a flourishing, growing democracy.
"I have agreed with my South African counterparts that South Africa is now in a position to fund its own development.
"It is right that our relationship changes to one of mutual co-operation and trade, one that is focused on delivering benefits for the people of Britain and South Africa as well as for Africa as a whole."
The UK gives South Africa around £19m a year in direct aid.
