Álvaro Xavier de Castro () was Prime Minister of Portugal from 20 November to 30 November 1920 and from 18 December 1923 to 6 July 1924.
Early career
He was born in Guarda, on 9 November 1878. He was part of the Constitutional junta that governed Portugal in 1915. He later served as Governor-General of Mozambique between 1915 and 1918. He was a prominent participant in the attempted coup of January 11, 1919 which took place after the assassination of Sidónio Pais.
Later career
He co-founded the National Reconstitution Republican Party. He was appointed Prime Minister, during a brief period (from 20 November to 30 November 1920). He was replaced by Liberato Pinto, an army officer.
He then joined a new party, the Nationalist Republican Party. He again became Prime Minister of Portugal, from 18 December 1923 to 6 July 1924. He died in Coimbra on 29 June 1928.