The Jewish communities of the Iberian Peninsula had an origin story that placed their arrival in the peninsula after the destruction of the first temple in Jerusalem by the Babylonian King Nebuchadnezzar II in 587 BCE. Actual archaeological evidence (mostly tombstones), however, only testifies to their presence in the Iberian Peninsula during the Roman Empire and it is more likely that Jewish communities gradually established themselves in the Roman province of Hispania as the exiled Jewish diaspora spread across the Mediterranean following the destruction of the Second Temple by the Romans in 70 CE. Although they were persecuted during the post-Roman period in which the Christian Visigothic kings ruled the peninsula, the Jewish communities flourished economically and culturally in the wake of the Muslim invasion in 711 and Islamic takeover of most of the Iberian Peninsula. When the Muslim Umayyad caliphate of Cordoba collapsed in 1031, the various Christian kingdoms of the north (Portugal, Castile–León, Navarre and the Crown of Aragón) slowly began to expand southwards and increasing numbers of Jews came under Christian rule.

Until the end of the fourteenth century, Jews, Christians, and Muslims living in the various Christian kingdoms of the Iberian Peninsula coexisted in their daily lives—what historians have described as convivencia—although interfaith tensions always existed. The Jews who came under Christian rule were granted the same status as Jewish communities elsewhere in Christian Europe and their inferior status (relative to the dominant Christians) was enshrined in laws that threatened fierce punishments for Jews (and Muslims) whose actions threatened the religious status quo. Nonetheless, the frontier conditions in the Iberian Peninsula continued to create favourable economic conditions for Jews as Christian rulers, short of resources and manpower in their newly conquered lands, were keen to protect their Jewish subjects and to offer them inducements to remain under their authority.

In comparison with the Jewish communities of other areas of Europe, the size of the Jewish population in the Iberian Peninsula appears to have been large. Although the available evidence is scant, it is sufficient to allow historians to confi-dently guestimate that there were around a quarter million Jews in Castile alone in the fourteenth century, a number that may well have approached three hundred thousand if Portugal and the lands of the Crown of Aragón are included.