"Her undisputed talent, her honesty and her profound convictions leave a great legacy to future generations," her family said in the statement posted on her website.
Known affectionately as La Negra, "the Black One" due to her dark hair and skin, Sosa fought South American authoritarian rulers with her voice.
Sosa's version of Violeta Parra's "Gracias a la Vida" - "Thanks to Life" - became an anthem for leftists around the world in the 1970s and 1980s.
Her own political leanings - she was a member of the Communist Party - attracted attention from the authorities between 1976-83, when up to 30,000 people were killed in a crackdown on leftist dissent.
She was forced into exile and her recordings were banned.
Sosa hailed from a working-class family in Argentina's poor, sugar-growing province of Tucuman.
She entered the music industry at the age 15, when friends, impressed by her talent, encouraged her to enter a local radio contest under the pseudonym "Gladys Osorio".
She won a two-month contract with the broadcaster, the first of many accolades over a career that continued until her final days.
"I didn't choose to sing for people," Sosa said in a recent interview on Argentine television. "Life chose me to sing."
Her latest album, "Cantora 1 & 2", a collaboration with artists including Shakira, Caetano Veloso, Jorge Drexler, has been nominated for three prizes in next month's Latin Grammy awards in Las Vegas.