The Spanish Inquisition published its first Index of Prohibited Books in 1551.
The first Spanish index was not created entirely from scratch. The Inquisition adopted the University of Leuven’s 1546 catalogue and issued it with an appendix covering books printed in Spanish. It appeared 13 years before Pope Pius IV promulgated the Roman Catholic Index in 1564.
The 1551 list targeted works considered heretical or dangerous to Catholic orthodoxy, especially writings associated with Protestant reformers. It also reflected growing anxiety about vernacular religious reading during the Reformation, when printing made controversial ideas much easier to circulate.
A common mix-up is 1559: that was the year Fernando de Valdés issued the second Spanish index, a much larger and more original compilation of roughly 700 books. Later editions appeared repeatedly, including major revisions in 1583–84, 1612 and 1632.