Winnie Madikizela-Mandela, prominent South African anti-apartheid activist and former wife of Nelson Mandela, has died at 81.

In a statement obtained by CBS on Monday, the family of Madikizela-Mandela wrote that she "died after a long illness, for which she had been in and out of hospital since the start of the year."

"She succumbed peacefully in the early hours of Monday afternoon surrounded by her family and loved ones," the statement continued.

The #Mandela Family statement on the Passing of #WinnieMandela. #RIPWinnieMandela. #SABCNews pic.twitter.com/u7O7sK8WdV— Thabiso Sithole (@ThabisoSithole) April 2, 2018

Many around the world are mourning the death of Madikizela-Mandela, who was known as "Mother of the Nation."

Rest in peace Mama Winnie Mandela. We will never forget you.

???????????? pic.twitter.com/sGkzZAuGlT

— #MamaKaBafana ???? (@nelisiwe_sibiya) April 2, 2018

Madikizela-Mandela was born on September 26, 1936, in what’s now known as the Eastern Cape province in South Africa. She began her career as a social worker in a hospital and met Nelson Mandela when she was 22 years old. The pair married in 1958 and had two children together.

Madikizela-Mandela and Nelson Mandela were married for 38 years, with Nelson Mandela notably imprisoned for 27 of those years. While Nelson Mandela was in prison, Madikizela-Mandela fought for the rights of black South Africans during the nation’s white minority rule.

In the statement, Madikizela-Mandela’s family said she was “one of the greatest icons of the struggle against apartheid.”

“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," the statement read. "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."

Winnie Mandela

Get relevant content delivered to you once a week