Spain: 'Madonna of the Catholic Monarchs'. Tempera on panel painting by Fernando Gallego (1440-1507) of Isabella I of Castile, c. 1490. Isabella I (Spanish: Isabel I, Ysabel, anglicised as Elizabeth) (22 April 1451 - 26 November 1504) was Queen of Castile and Leon. She and her husband Ferdinand II of Aragon brought stability to both kingdoms that became the basis for the unification of Spain. Later the two laid the foundation for the political unification of Spain under their grandson, Charles V, Holy Roman Emperor.