Alfredo Luís da Costa (24 November 1883 – 1 February 1908) was a Portuguese publicist, editor, journalist, shop assistant and salesman who was part of the Portuguese Carbonária and a Mason, best remembered for being one of the two assassins (with Manuel Buíça) credited in the assassination of King Carlos I of Portugal and the Prince Royal, Luis Filipe, during the events that became known as the 1908 Lisbon Regicide (on 1 February 1908), ultimately leading to his death.

On meeting Alfredo Luís, Raul Pires described him as "...of a serious physiognomy, almost tragic" and with "big brown eyes, slow-moving, with a stance that appeared sleep-walking...with a moustache on his face, the nose lightly bent to the left.

While in Angra, he was also the driving force behind the Núcleo da Juventude Anarco-Sindicalista (English: Center for Anarchist-Syndicalist Youth)[2] He continued his career in 1903, in Estremoz, where he was a republican propagandist, contributing to local newspapers with an unlimited dedication.

On the disastrous evening of the Municipal Library Elevator Coup (28 January 1908)[3] Costa lead a group of 20 men (with Manuel Buiça) to assault the Royal Palace of Necessidades, but modified their strategy and, instead, attacked the Quartel dos Lóios.

Planned, financed and armed by elements of the Portuguese Republican and Progressive Dissidency Parties, the coup d'etat was to be carried out by members of the Carbonária, Formiga Branca and masonry in order to proclaim a Republic and/or assassinate Prime Minister João Franco.

During an encounter with Machado Santos and Soares Andrea at the Café Gelo, shortly after the attempted coup, he affirmed: This refrain was followed by a conspicuous patting of his coat, where he carried his Browning revolver.

On the morning of 1 February 1908, Alfredo Costa met with Manuel Buíça and other Carbonárias in the Quinta do Xexé, in Olivais, where they finalized the assassination of João Franco and members of the Royal Family.

[4] It is unclear when the decision was made to kill the King, but it was part of the instructions given to the cell that Alfredo Costa and Manuel Buíça belonged to, during the Elevator coup attempt.

[10] After the establishment of the Republic, the same Association acquired land in the cemetery in order to construct a monument to the heroic liberators of the Fatherland (as written on the request to the Lisbon city hall authorities in their petition).

The final report into the assassination of King Carlos and Prince Royal, which was ready for judicial investigation disappeared (on 25 October 1910), shortly after the proclamation of the First Portuguese Republic.

Judge Almeida e Azevedo submitted the process to Dr. José Barbosa, member of the Provisional Government, who was responsible for delivering it to Afonso Costa, the new Minister of Justice.