The South African anti-apartheid campaigner Winnie Madikizela-Mandela has died, aged 81, her personal assistant confirmed.
Her family said she died “peacefully” after a long illness.
They said the former wife of the late Nelson Mandela had been “in and out of hospital since the start of the year”.
In a statement, her family said: “Mrs Madikizela-Mandela was one of the greatest icons of the struggle against apartheid. She fought valiantly against the apartheid state and sacrificed her life for the freedom of the country.
“Her activism and resistance to apartheid landed her in jail on numerous occasions‚ eventually causing her banishment to the small town of Brandfort in the then Orange Free State.
“She kept the memory of her imprisoned husband Nelson Mandela alive during his years on Robben Island and helped give the Struggle for justice in South Africa one its most recognisable faces.
“She dedicated most of her adult life to the cause of the people and for this was known far and wide as the Mother Of The Nation.”
They urged supporters to celebrate the gift of her life.
Although she suffered with bad health this year, she still attended her church’s Good Friday service, and campaigned with ANC president Cyril Ramaphosa during a voter registration drive last month.
Tributes have been paid across the world following Mrs Madikizela-Mandela’s death, while South African politicians have been arriving at her Soweto home to pay their respects.
Retired South African archbishop and Nobel laureate Desmond Tutu led the tributes, saying said she was “a defining symbol of the struggle against apartheid”.
“She refused to be bowed by the imprisonment of her husband, the perpetual harassment of her family by security forces, detentions, bannings and banishment,” he said.
“Her courageous defiance was deeply inspirational to me, and to generations of activists.”
Labour peer Peter Hain, who was born in South Africa and was a leading figure in the British anti-apartheid movement, tweeted his support for Winnie.
New South African president Cyril Ramaphosa described her as the “voice of defiance”.
Mrs Madikizela-Mandela was married to Nelson Mandela for nearly four decades until 1996.
He spent much of their marriage in prison, and she campaigned tirelessly for his release, eventually securing on 11 February 1990.
Mrs Madikizela-Mandela was convicted in 1991 of killing an activist named Stompie Seipei who was found near her home with his throat cut.
She was sentenced to six years in prison, but it was reduced on appeal.
The couple separated in 1992, and he sacked her from his cabinet three years later after allegations of corruption. She took her new surname, Madikizela-Mandela, after their divorce.
She built her own role as a grassroots activist, completing university at a time when very few black women in South Africa did so, and was politicised by her work as a social worker in a Johannesburg hospital.
Despite controversy and convictions, she was able to rehabilitate her political career, winning a seat in the 2009 elections.
She once accused her former husband of agreeing to a “bad deal for the blacks” but was a regular visitor to his bedside and even with him when he died.
Mrs Madikizela-Mandela and Mr Mandela had two daughters.
British actor Idris Elba tweeted: “Rest in peace Mama Winnie. My heart is heavy right now. You lived a full and important life contributing to the liberation of a nation by force and ACTUAL ACTIVISM. You will never be forgotten.”
Reverend Jesse Jackson Sr, an American civil rights figure, tweeted: “In the darkest hours of the struggle to free South Africa, with Nelson Mandela in prison, the face of hope and courage was Winnie Mandela. May she forever rest in power.”
British singer Estelle tweeted: “She lived for everyone, fought for lives and empowered along the way. RIP to a revolutionary, Winnie Mandela!”