Winnie was imprisoned multiple times from 1969 and she spent much of her spells in solitary confinement.
She had been treated for diabetes and underwent major surgeries as her health began failing over the past several years.
Since Monday's announcement, many have expressed their sadness over Madikizela-Mandela's passing and their admiration for her work, including members of the African National Congress, who said in a statement to the BBC, "With the departure of Mama Winnie, [we have lost] one of the very few who are left of our stalwarts and icons".
Additional reporting from Newsy affiliate CNN.More news: Trump blasts Amazon for hurting the postal service. Is that true?
As the mother of two of Mandela's children, Madikizela-Mandela and her ex-husband appeared to rebuild a friendship in his final years.
The Democratic Alliance's Mmusi Maimane said: "It is a deeply sad occasion for the people of South Africa". She had also suffered from diabetes for some years. Her marriage to Mr Mandela broke down in the years after his release and they were divorced in 1996. However, her controversial statements promoted violence and she was accused in a murder case and a convict in bank fraud case.
In May 1991 she was sentenced to six years in prison for kidnapping in relation to the incident, but the sentence was later reduced to a fine. When Madiba was released in 1999, she said that he could not be guarded by De Klerk's security.
Ms Madikizela-Mandela will be honoured by a state funeral on April 14, preceded by an official memorial service on April 11, said President Cyril Ramaphosa after visiting her home in Johannesburg's Soweto township on Monday evening.
In 1990 the world watched when Nelson Mandela finally walked out of prison - hand in hand with Winnie.More news: Tim Cook casts corner-office shade on Mark Zuckerberg
Outside Africa, Madikizela-Mandela was known largely because of her ex-husband, but in South Africa she was the mouthpiece and face of the bitter struggle against the racist regime.
"They say life can never be the same after the death of one's mother, irrespective of your relationship with her".
At the ANC conference in 2007, she was elected to the party's top decision-making body, the National Executive Committee, and in the 2009 general election, she was placed fifth on the list of ANC MPs nominated for parliament, in a clear sign that then-President Jacob Zuma saw her as an electoral asset.
But she was a unifying force for some members of the ANC, and had this connection of not only being a national and worldwide figure, but also maintaining very close, personal ties, particularly in Soweto.
After blacks rioted in the segregated Johannesburg township of Soweto in 1976, Madikizela-Mandela was again imprisoned without trial, this time for five months.More news: Trump's Amazon Tweets Dent His Stock Market Bragging Rights
It was not unusual to see him at public events with her on one side and his third wife, Graca Machel, on the other. "He loved her to the end".
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