President Jacob Zuma sent condolences to the family of Caroline Motsoaledi, wife of Rivonia trialist Elias.
“We have learnt the news of her passing with great sadness. She was a pillar of strength to our leader comrade [Elias] Motsoaledi and has been an activist in her own right,” Mr Zuma said in a statement on Wednesday.
“She endured detention without trial, remained steadfast in support of the struggle inside of all the harassment the regime inflicted on her, and continued against all odds to hold the family together in their commitment to the struggle.”
Motsoaledi died in hospital on Tuesday.
She had six children with her husband Elias Motsoaledi, who was one of the Rivonia Trialists and was sentenced to life imprisonment on Robben Island.
The Rivonia Trial took place between 1963 and 1964. Ten leaders of the ANC were tried for 221 acts of sabotage designed to overthrow the apartheid system.
Earlier, the ruling party said Motsoaledi was an ANC member who worked closely with other stalwarts including Albertina Sisulu and Winnie Madikizela-Mandela.