The Alhambra Decree (also known as the Edict of Expulsion; Spanish: Decreto de la Alhambra, Edicto de Granada) was an edict issued on 31 March 1492 by the joint Catholic Monarchs of Spain, Isabella I of Castile and Ferdinand II of Aragon, ordering the expulsion of unconverted Jews from the Crowns of Castile and Aragon and its territories and possessions by 31 July of that year. Its primary purpose was to eliminate the influence of the remaining Jews on Spain's large converso New Christian population, converted from Judaism, to minimize the possibility that the latter and their descendants would be able to secretly practice their former faith.
Over half of Spain's Jews had converted as a result of the religious persecution and pogroms which occurred in 1391. Due to continuing attacks, around 50,000 more had converted by 1415. A further number of those remaining chose to convert to avoid expulsion. As a result of the Alhambra Decree and persecution in the years leading up to the expulsion of Spain's estimated 300,000 Jewish origin population, a total of over 200,000 had converted to Catholicism in order to remain in Spain, and between 40,000 and 100,000 remained Jewish and suffered expulsion. An unknown number of the expelled eventually succumbed to the pressures of life in exile away from formerly-Jewish relatives and networks back in Spain, and so converted to Catholicism to be allowed to return in the years following expulsion.