José Júlio da Costa (14 October 1893, Garvão – 16 March 1946, Lisbon) was a Portuguese left-wing political activist who assassinated President Sidónio Pais of Portugal on 14 December 1918.

In a few interviews that José gave before his death, he said that he was discontent with Pais 's policy and even accused him of betraying the ideals of the Portuguese Republican Revolution of 1910 and adapting from Germany, alongside the monarchists and clergy, who were the enemies of the Republic.

He became radicalized and vowed to avenge his countrymen and fellow soldiers by assassinating the one he felt was the cause of all their problems, President, or, as he called him, President-King Pais.

A panic erupted in the station, but José made no attempt to escape and was arrested moments after he had fired and had been brutally beaten by the crowd.

The President was still alive and rushed to a hospital, but the second shot, which had hit him in the stomach, proved to be fatal, and he died shortly before midnight on 14 December 1918.

José never stood trial for his actions and was locked away for 28 years in a psychiatric hospital in Lisbon in which he was forgotten by the government and fell into obscurity.