The ANC Youth League (ANCYL) said it is "shattered" and "saddened" by the death of struggle stalwart Winnie Madikizela-Mandela.
"We mourn the passing of our mother in these trying times, as Mama Winnie has left an immense void among South Africa’s youth, whom she loved dearly," secretary general Njabulo Nzuza said in a statement on Tuesday.
Madikizela-Mandela died in Milpark Hospital in Johannesburg on Monday, at the age of 81, after a long illness.
The youth league described Madikizela-Mandela as "Seaparankwe"- loosely translated as "one who wears the plumes of the rare bird".
The ANCYL said Madikizela-Mandela had been a fierce revolutionary in her own right.
"Mama Winnie remains one of the struggle's great icons to have contributed immensely in waging the struggle against apartheid.
"Her struggles and tribulations are succinctly described by her first name Nomzamo, which means 'she who must endure trials'.
"She stood against the system that continued to brutalise black people. She was officially banned under draconian laws intended to make her persona-non-grata, unable to work, socialise, and move freely."
The ANCYL said her contribution to the struggle had led to a free South Africa.