Mercedes Sosa (Haydée Mercedes Sosa), (born July 9, 1935, San Miguel de Tucumán, Arg.—died Oct. 4, 2009, Buenos Aires, Arg.), Argentine folk singer who was known as “the voice of the voiceless” for her songs that spoke of the struggle for economic and political justice. She was a leading proponent of the nueva canción movement of the 1960s, which used traditional music to express political themes. Sosa, who possessed a powerful and dramatic alto voice, was known as a peerless interpreter of songs written by others. Her first album, La voz de la zafra, appeared in 1959, but it was her 1965 performance at Argentina’s national folklore festival in Cosquín that brought her national attention and increasing popularity. After the military took power in 1976, she was subject to official harassment that culminated in the public arrest of Sosa, her band, and much of her audience at a concert in 1979. Sosa went into exile, during which time she began to expand her repertoire to include other forms of popular music; she returned to Argentina in 1982. She won Latin Grammy Awards for best folk album in 2000 for Misa Criolla, in 2003 for Acústico, in 2006 for Corazón libre, and in 2009 for Cantora Vol. 1.