"Madiba [the name of the Xhosa tribe to which Mandela belongs] is special to South Africa in many ways, having dedicated his entire adult life to the relentless fight for freedom, democracy, peace and stability in our country," government officials said in a statement.
The date of his birth also is Nelson Mandela International Day.
At 94, "Madiba is almost as old as the African National Congress itself -- the movement to which he dedicated his entire adult life and a movement that is celebrating its centenary throughout 2012," the statement said.
The statement said the South African government is committed "to continuing President Mandela's legacy and will continue the long walk to confront poverty, unemployment and inequality."
President Barack Obama, on behalf of the United States, extended congratulations to Mandela.
"Mandela's extraordinary life and steadfast commitment to the principles of democracy and reconciliation continues to be a beacon for people of all backgrounds who strive for dignity, justice and freedom," Obama and his wife, Michelle, said in a statement. "By any measure, Nelson Mandela has changed the arc of history, transforming his country, continent and the world."
In 2009, the United States joined 192 U.N. member countries to create Nelson Mandela International Day.
"On this important occasion, we honor Madiba's commitment to service and the betterment of our communities," Obama said. "There is no more fitting tribute to a man who has demonstrated to the world the extraordinary power of non-violence, of tolerance and of unwavering service to our fellow men and women."