Francisco Manuel Lumbrales de Sá Carneiro, GCTE, GCC, GCL (Portuguese: [fɾɐ̃ˈsiʃku sa kɐɾˈnɐjɾu]; 19 July 1934 – 4 December 1980) founded the Portuguese Social Democratic Party in 1974 (the year of the Portuguese Carnation Revolution) and was elected Prime Minister of Portugal in January 1980, but only held office for eleven months, dying in a plane crash with his partner, "Snu" Abecassis (born Ebba Merethe Seidenfaden), on 4 December 1980. A parliamentary inquiry said in 2004 that there was evidence of a bomb in the aircraft, after a 1995 inquiry had concluded there was evidence of sabotage.
Sá Carneiro was born in Porto, Vitória, the third of the five children of lawyer José Gualberto Chaves Marques de Sá Carneiro (born 31 August 1897 in Barcelos) and wife Maria Francisca Judite Pinto da Costa Leite (born 29 March 1908) of the Counts of Lumbrales in Spain.
A lawyer by training, Sá Carneiro became a member of the puppet National Assembly in 1969 and, in turn, one of the leaders of the "Liberal Wing" which attempted to work for the gradual transformation of António de Oliveira Salazar's dictatorship into a Western European democracy.