King of Portugal, born at Lisbon; usurped the throne in defiance of the right of his brother, Don Pedro, emperor of Brazil, who, however, conceded to him the title of regent on condition of his marrying Donna Maria, his daughter; on his arrival in Portugal he had himself proclaimed king, but refused to marry Maria, who followed him, and prohibited her landing, which, together with his conduct of affairs, provoked a civil war, in which the party of Don Pedro prevailed, and which ended in the capitulation of the usurper and his withdrawal to Italy (1802-1866).