Bishop Stephen Peter Alencastre, SS.CC. (born Estêvão Pedro de Alencastre; November 3, 1876 – November 9, 1940) was a Roman Catholic bishop who served as the fifth and last Vicar Apostolic of the Vicariate Apostolic of the Hawaiian Islands (now the Roman Catholic Diocese of Honolulu). He was also an apparent titular bishop of Arabissus.