The Spanish Inquisition was an ecclesiastical tribunal started in 1478 by Catholic Monarchs Ferdinand II of Aragon and Isabella I of Castile for the newly united Kingdom of Spain.

The first Spanish ambassador to Rome, Gonzalo de Beteta, was appointed in 1480, thus establishing the oldest permanent diplomatic mission in the history of the world.

These included Vatican support for the Granada War, the partition of the New World between Spain and Portugal via the “Bula Inter Caetera” in 1493 (see Treaty of Tordesillas), and the creation of the Holy League, which led to a key victory for Christendom at the Battle of Lepanto.

The relations of the Holy See with the recent Zapatero's PSOE government were strained because of legislation allowing for same-sex marriage and liberalisation of abortion, the end of religious education in public schools, and general political support for secularism.

This contrasts with previous Spanish administrations, many of which had been keen on promoting Spain's historic Catholic culture and identity, such as under Francisco Franco, for example.