There is a long history of Jewish conversion to Catholicism, both voluntarily and forced conversion. What follows is a partial history of some of the well known forced conversions.

Jewish Christians were the followers of a Jewish religious sect that emerged in Judea during the late Second Temple period (first century AD). These Jews believed Jesus to be the prophesied Messiah, but maintained the observance of Jewish law.^[1]

Forced conversions of Jews were carried out with support of rulers during Late Antiquity and the early Middle Ages in Gaul, the Iberian peninsula and in the Byzantine empire.^[2]

Royal persecutions of Jews from the late eleventh century onward generally took form of expulsions, with some exceptions, such as conversions of Jews in southern Italy of the 13th century, which were carried out by Dominican Inquisitors but instigated by King Charles II of Naples.^[2]

Jews were forced to convert to Catholicism before and during the First Crusade by the Crusaders in Lorraine, on the Lower Rhine, in Bavaria and Bohemia, in Mainz and in Worms.^[3]

Over a hundred thousand of Spain's Jews converted to Catholicism as a result of pogroms in 1391.^[4] Those remaining practicing Jews were expelled by the Catholic monarchs Ferdinand and Isabella in the Alhambra Decree in 1492, following the Catholic Reconquest of Spain. As a result of the Alhambra Decree and persecution in prior years, over 200,000 Jews converted to Catholicism and between 40,000 and 100,000 were expelled.^[5]

Meanwhile, in Portugal, although an order for their expulsion was given in 1496, only a handful were allowed to leave, the rest being forced to convert.^[2]

Between 1648 and 1649, a large-scale uprising of Cossacks and Ukrainian peasants led by Bohdan Khmelnytsky swept through the Polish–Lithuanian Commonwealth, the area of today's Ukraine. In the course of the fighting, there were many Jewish casualties, and many Jewish communities were destroyed. A large number also converted to Eastern Orthodoxy.

In the 18th century, Elizabeth of Russia launched a campaign of forced conversion of Russia's non-Orthodox subjects, including Muslims and Jews.^[6]

Also, in the second half of the 18th century, a mass conversion to Catholicism occurred by followers of Jacob Frank.^{[citation needed]}

Although forced conversions were less common in the 20th century, missionary activity remained strong, and many Jews chose to convert in order to integrate into secular society. A critical period in Britain followed when many of the chief Sephardic families — including the Bernals, Furtados, Ricardos, Disraelis (most prominently, Benjamin Disraeli twice prime minister of the United Kingdom), Ximenes, Lopezs and Uzziellis joined the church.^[7][8]

Various estimates have been put forward as to the total number of conversions during the 19th century. One Catholic encyclopedia writes that the number exceeded 100,000;^[13] while the Jewish Encyclopedia records approximately 190,000.^[14] Other contemporary sources put the number at 130,000^[15] or even as many as 250,000.^[16]

As a result of the high rate of conversion, many Catholics can be found with a measure of Jewish parentage. In 1930s Germany, Nazi officials discovered that the German Catholic population with some level of Jewish ancestry almost equalled that of the Jewish community of just over five hundred thousand.^[17]

Today, according to 2013 data from the Pew Research Center, about 1.6 million adult American Jews identify themselves as Christians, most of them Protestant.^[18][19][20] Of those, most were raised as Jews or are Jews by ancestry.^[19] According to a 2012 study 17% of Jews in Russia identify themselves as Christians.^[21][22] According to a 2020 study by the Pew Research Center, 19% of those who say they were raised Jewish in the United States, consider themselves Christian.^[23]

• Conversion of the Jews (future event)