"Gal Costa was one of the greatest singers in the world, one of our main artists in taking the name and sounds of Brazil all over the planet; her talent, technique and audacity enriched and renewed our culture; Gal formed and marked the lives of millions of Brazilians," he said in a statement.
Brazilian Popular Music Icon Gal Costa Dies at 77
The leader of the Brazilian left recalled that the country lost one "of its great voices" but stressed that his legacy, his work and the memory of her songs would be eternal.
On social networks, Lula accompanied his note of sorrow dedicated to family, friends and admirers with a photo in which both appear embracing.
Costa, whose career flourished during the Brazilian military dictatorship (1964-1985), always held progressive positions and, in the recent elections, openly called for a vote for Lula to defeat President Jair Bolsonaro.
Former President Dilma Rousseff (2011-2016) also expressed her sorrow at the passing and said that Costa's joy and charm were a refuge "for bright and dark days throughout five decades."
"She is a giant of Brazilian Popular Music (MPB)," he stressed, adding, "I feel immense sadness to see that great star leave us just now, at the instant when we regain hope for better days."
Big names in Brazilian music, such as Gilberto Gil, Caetano Veloso and Maria Bethânia, with whom she once formed the group "Doces bárbaros," also expressed their sorrow on social networks.
President Bolsonaro, who has only broken his silence on two occasions since he lost the elections last October 30, did not comment on the death of the singer, one of the most beloved in Brazil.