Gold Fields on Wednesday said Ramphele had decided to retire "to further her socioeconomic and political work". Former South African Airways chairperson Cheryl Carolus will succeed Ramphele as chair, the company said.
"I am pleased that during my tenure at Gold Fields significant progress has been made in entrenching the sustainability of the company's operations worldwide. I also believe that the separate listing and unbundling of the company's KDC [Kloof Driefontein Complex] and Beatrix mines into Sibanye Gold will provide the South African operations with the dedicated and focused management as well as full control over their cash flows to extend their life of mine in a sustainable manner to the benefit of investors, employees and communities," Ramphele said in a statement.
"She is an amazingly powerful woman," said political analyst Nic Borain, adding that Ramphele would not be taking a leap into direct politics against the might of Nelson Mandela's 100-year-old liberation movement without having a solid plan in place.
"She would have done her homework," he said.
Another political analyst, Allister Sparks, said a Ramphele-led party would be likely to take votes from the ANC rather than the Democratic Alliance.
"She is not just a fine academic; she is a dynamic woman of action," he wrote in an editorial in Wednesday's Business Day.
A consultancy working for Ramphele said she would be making a statement about her political plans on Johannesburg's Constitution Hill on Monday.
A threat as opposition
In late January Ramphele expressed, while on a visit to the United States, her intention to join politics. During her visit to the US, Ramphele said she was collecting money for a political party and said she was "entering politics to save her country", the Rapport said.
Last week the Mail & Guardian reported that ANC and the Democratic Alliance were not threatened by Ramphele's possible move to politics.
"We have a 60-year legacy upon which we drive the issue of ensuring a better life for all South Africans. At the moment she has none of that base, no platform to build on," DA spokesperson Mmusi Maimane told the Mail & Guardian.
Maimane added that even though Ramphele would appeal to black urban middle class voters – a key target of the DA in the 2014 general election – the party was not concerned about losing votes.
"We've been growing in rural areas and I would be surprised if the Mamphela Ramphela brand is even heard of in those constituencies," he added. "She will do well but I don't think we are too worried about what the prospects of her forming a political party will do to our voter base."
At the time, ANC secretary general Gwede Mantashe said the ANC has a proven track record of governance from which to draw on when attracting voters, while Ramphele will only be calling on her past as an anti-apartheid campaigner.
"It remains to be seen if what she created – or will create – changes anything. We will contest elections against anyone and are confident we will succeed," Mantashe said.
'Agent of change'
The M&G reported in January that DA leader Helen Zille tried to get Ramphele to join her party last year, but she declined and formed the Citizens' Movement, a nongovernmental organisation. She said at the time that she had never joined a political party in her life. "I am not a joiner but a change agent. I have always seen my role as a change agent supporting any appropriate transformative process initiated by any South African," she said.
Ramphele (65) commands considerable respect as a partner of Black Consciousness leader Steve Biko, who died in 1977 as a result of beatings received in an apartheid prison.
She was also placed under house arrest for seven years by South Africa's apartheid government because of her political activities.
Ramphele was appointed to the board of Gold Fields on July 1 2010 and chaired the board from November 2 2010. She also served on various board committees during her tenure. – Additional reporting by Reuters