Nelson Mandela's ex-wife, Winnie Madikizela-Mandela, has died at the age of 81

The South African anti-apartheid activist and former wife of Nelson Mandela passed away at the Netcare Milpark Hospital in Johannesburg.

Her personal assistant, Zodwa Zwane, confirmed on April 2, 2018, that the cause of death was described as "a long illness." Additional details have not yet been released to the public.

She also had diabetes and her family's spokesperson, Victor Dlamini, added that she "had been in and out of the hospital since the start of the year."

As reported by ABC News, she was hospitalized for a kidney infection. Madikizela-Mandela, affectionately known as the Mother of the Nation and Mama Winnie, was 81 years old.

Madikizela-Mandela met former President Nelson Mandela at a bus stop in Soweto in 1957 when she was 21 years old. The couple walked down the aisle in 1958.

They had two daughters. Zenani was born in 1959 and Zindziwa in 1960. In 1963, Nelson Mandela was arrested and jailed for 27 years, for conspiracy to overthrow the Apartheid government.

Throughout his imprisonment, Winnie Mandela campaigned for his release while continuing to fight for the human rights of black South Africans.

She was regularly detained by the National Party, tortured, and held in solitary confinement for more than a year. She was also exiled to a town in the Orange Free State.

During that time she organized local clinics and received the Robert F. Kennedy Human Rights Award in 1985 for her contributions towards human rights in South Africa.

Nelson Mandela was released from prison in 1990, and the couple separated two years later. Their divorce was finalized in 1996.

She was portrayed by actress Naomie Harris in the 2013 film, Mandela: Long Walk To Freedom, and said that it was the first time her story had been accurately captured on film.

She was Deputy Minister of Arts, Culture, Science, and Technology from 1994 until 1996, as well as a Member of Parliament from May 2009 until her death.