Vilma Espin, the wife of Cuban Defense Minister Raul Castro, died on Monday at the age of 77.
The official Cuban state television reported that Espin died from complications from a long illness.
Born into a wealthy family in Santiago in 1930, Espin became engaged in early student movements against right-wing dictator Fulgencio Batista in her hometown.
In 1959, Espin married Raul Castro in Havana. A year later, under Castro's instructions, she founded the Cuban Women's Federation, a mass organization that aimed to advance the revolutionary cause and gender equality.
She died as a member of the Communist Party's Central Committee and a member of the Council of State.
Cuba's Council of State declared one day of official mourning in Espin's honor. Top Cuban leaders will pay homage to Espin on Tuesday night at the Karl Marx theater in Havana.