New Christian (Spanish: cristiano nuevo; Portuguese: cristão-novo; Catalan: cristià nou) was a law-effective and social category developed from the 15th century onwards, and used in what is today Spain and Portugal as well as their New World colonies, to refer to Sephardi Jews and Muslims ("Moors") who had converted to the Catholic Church, often by force or coercion. It was developed and employed after the Reconquista of the Iberian Peninsula by the Catholic Monarchs. By law, the category of New Christian included not only recent converts, but also all their known baptized descendants with any fraction or quantum of New Christian blood up to the fourth generation, and then in Phillip II's reign it included any person with any fraction of New Christian blood "from time immemorial". In Portugal, it was only in 1772 that Sebastião José de Carvalho e Melo, 1st Marquess of Pombal, finally decreed an end to the legal distinction between New Christians and Old Christians.
Although the category of New Christian is meaningless in Christian theology, it was nevertheless introduced by the Old Christians who claimed "pure unmixed" Spanish European bloodlines.
The Old Christians wanted to legally and socially distinguish themselves from the New Christian conversos (converts to Christianity), who they considered to be tainted by virtue of their non-Spanish bloodlines, even though in the case of Muslims, the overwhelming majority of Spain's Muslims were also of indigenous Iberian stock, themselves the descendants of native Iberians who earlier converted to Islam under Muslim rule.
In practice, for New Christians of Jewish origin, the conception of New Christian was a legal mechanism and manifestation of racial antisemitism, being a prejudice against Jews as a racial/ethnic group, rather than Judaism as a religion. For those of Moorish origin, it was a manifestation of racial anti-Berberism and/or anti-Arabism.
The related Spanish development of an ideology of limpieza de sangre (cleanliness of blood) also excluded New Christians from society — universities, emigration to the New World, many professions — regardless of their sincerity as converts.
Other derogatory terms applied to each of the converting groups included marranos (i.e. "pigs") for New Christians of Jewish origin, and moriscos (a term which carried pejorative connotations) for New Christians of Andalusian origin.
Aside from social stigma and ostracism, the consequences of legal or social categorization as a New Christian included restrictions of civil and political rights, abuses of those already-limited civil rights, social and sometimes legal restrictions on who one could marry (anti-miscegenation laws), social restrictions on where one could live, legal restrictions of entry into the professions and the clergy, legal restrictions and prohibition of immigration to and settlement in the newly colonized Spanish territories in the Americas, deportation from the colonies.
In addition to the above restrictions and discrimination endured by New Christians, the Spanish Crown and Church authorities also subjected New Christians to persecution, prosecution and capital punishment for actual or alleged practice of the family's former religion.
After the Alhambra Decree of expulsion of the Jewish population from Spain in 1492 and a similar Portuguese decree in 1497, the remaining Jewish population in Iberia became officially Christian by default. The New Christians, especially those of Jewish origin, were always under suspicion of being judaizantes ("judaizers"), that is, apostizing from the Christian religion and being active crypto-Jews.
Despite the discrimination and legal restrictions, many Jewish-origin New Christians found ways of circumventing these restrictions for emigration and settlement in the Iberian colonies of the New World, by falsifying or buying "cleanliness of blood" documentation, or attaining perjured affidavits attesting to untainted Old Christian pedigrees. The descendants of these, who could not return to Judaism, became the modern-day Christian-professing Sephardic Bnei Anusim of Latin America (it is only in the modern era that a nascent community, the Neo-Western Sephardim, is currently returning to Judaism from among this population).
Also as a result of the unceasing trials and persecutions by the Inquisition, other Jewish-origin New Christians opted to migrate out of the Iberian Peninsula in a continuous flow between the 1600s to 1800's towards Amsterdam, and also London, whereupon in their new tolerant environment of refuge outside the Iberian cultural sphere they eventually returned to Judaism. The descendants of these became the Spanish and Portuguese Jews (also known more ambiguously in the Netherlands as Spanish and Portuguese Jews, among other names elsewhere).
Although Iberian Muslims were protected in the treaty signed at the fall of Granada, and the New Christian descendants of former Muslims weren't expelled until over a century later, even so, in the meantime, different waves of Iberian Muslims and New Christians of Moorish origin left and settled across North Africa and the Ottoman Empire.
Throughout the Middle Ages, Sephardim (Iberian Jews) and Moros (Iberian Muslims) sometimes converted to Christianity, usually as the result of coercion: physical, economic, and social pressures.
In the 14th century there was increasing pressure, especially against the Jews, that culminated in the riots of 1391 in Seville and other cities in which many Jews were massacred. These riots caused the destruction of the Aljamas (Jewish quarters) of the cities and sparked many conversions, a trend that continued throughout the 15th century.
Unlike the other Iberian kingdoms, Portugal was not much affected by the waves of riots. However, there, the Jews remaining on Portuguese soil were forcefully converted in 1497, after which New Christians became a numerous part of the population.
The governments of Spain and Portugal created the Spanish Inquisition in 1478 and the Portuguese Inquisition in 1536 as a way of dealing with social tensions, supposedly justified by the need to fight heresy. Communities believed correctly that many New Christians were secretly practicing their former religions to any extent possible, becoming crypto-Jews and crypto-Muslims.
After conversion, New Christians of Jewish origin generally adopted Christian given names and Old Christian surnames. Eventually, all Old Christian given names and surnames were in use by New Christians of Jewish origin.
Among descendants of Sephardic Jews today, there are three categories of descendants:
Generally, it is only those who descend from group 1 who carry surnames which typically identify the surname-carrier as a person of Jewish origins. The other descendants of Sephardic Jews (those from group 2, and especially those from group 3) almost always carry "Old Christian" Spanish or Portuguese surnames because they became nominal Christians, whether intermittently or permanently.
For group 3 especially, only a very and extremely limited number of surnames carried by modern-day Spanish, Portuguese, Hispanics and Brazilians who descend from Jewish New Christians are surnames which are exclusively Jewish "New Christian" surnames being capable of, on their own, indicating Jewish origins of the surname-carrier. The great majority of their surnames are, per se, Old Christian surnames, and these surnames alone cannot indicate a Jewish origin without accompanying genealogical documentation, family traditions and customs, and/or Genealogical DNA testing.
Although it is true that a few surnames became popularly adopted by New Christians (including, for example the surname Pérez, because of its similarity to the Hebrew surname Peretz), such popularly adopted surnames by New Christians remain Old Christian surnames in origin, and carrying these surnames does not indicate Jewish ancestry by itself.
This phenomenon is much the same as is the situation with surnames which are typically considered to be Ashkenazi "Jewish" surnames. Most "Jewish" surnames among Ashkenazi Jews are not in fact "Jewish" per se, but are simply German or Slavic surnames (including so-called "Jewish" names like "Goldberg") which were adopted by Ashkenazi Jews, some of which became so overwhelmingly carried by Jews that they came to be seen as "Jewish", although there are gentile carriers of those same surnames, because it is with those gentile families that the surnames originated to begin with. Only some surnames found among Ashkenazi Jews today are surnames which are exclusively "Jewish" surnames being capable of, on their own, indicating Jewish origins of the carrier.