Antonio Joaquim Granjo (Chaves, 27 December 1881 – Lisbon, 19 October 1921; [ãˈtoniu ˈɡɾãʒu]) was a Portuguese lawyer and politician.
Already a committed republican from his youth, well before the 1910 overthrow of the monarchy, Granjo became a member of the National Constituent Assembly, elected on 28 May 1911. He gave up his constituency in order to join the army; during Portuguese participation in World War I, he saw combat himself, and upon returning home he wrote a book about his battle experiences.
After President Sidonio Pais was shot dead, Granjo took action against the Monarchy of the North, an attempt to restore a royalist regime in the north of Portugal, in 1919. He was President of the Municipal Chamber of Chaves, from February to July 1919. That same year he was elected to the Chamber of Deputies, by the Evolutionist Party, later being a founder of its successor movement, the Republican Liberal Party. Minister of Justice during Domingos Pereira's coalition government, he served two brief terms as Prime Minister, the first time, from 19 July to 20 November 1920, in a liberal government. Afterwards he was nominated Prime Minister again, to take the place of another liberal, Tome de Barros Queiros, on 30 August 1921.
During the infamous "Noite Sangrenta", on 19 October 1921, Granjo was assassinated. The political affiliation of his murderers is still a matter of dispute. That same night, two other prominent republicans of moderately right-wing sympathies, Machado Santos (widely known as the founder of the republic) and Carlos da Maia, also lost their lives.