Ashkenazi Jews are a Jewish diaspora population that formed in the Holy Roman Empire around the end of the first millennium CE. They traditionally speak Yiddish, since their migration to northern and eastern Europe in the late Middle Ages due to persecution. The term "Ashkenazi" was initially used to define a distinct cultural group of Jews who settled in the 10th century in the Rhineland in western Germany. Although strictly speaking, “Ashkenazim” refers to Jews of Germany, the term has come to refer more broadly to Jews from Central and Eastern Europe.

In a religious sense, an Ashkenazi Jew is any Jew whose family tradition and ritual follow Ashkenazi practice. In an ethnic sense, an Ashkenazi Jew is one whose ancestry can be traced to the Jews who settled in Central Europe. The vast majority of Ashkenazi Jews relocated to the Polish Commonwealth (today’s Poland, Lithuania, Latvia, Ukraine, and Belarus), where princes welcomed their skilled and educated workforce.

Today, Ashkenazi Jews are the Jewish ethnic identity most readily recognized by North Americans. Although the first American Jews were Sephardic, today Ashkenazim are the most populous ethnic group in North America. The modern religious denominations developed in Ashkenazic countries, and therefore most North American synagogues use the Ashkenazic liturgy.

In summary, Ashkenazi Jews are a Jewish diaspora population that formed in the Holy Roman Empire around the end of the first millennium CE. They traditionally speak Yiddish and migrated to northern and eastern Europe in the late Middle Ages due to persecution. The term "Ashkenazi" was initially used to define a distinct cultural group of Jews who settled in the 10th century in the Rhineland in western Germany, but it has come to refer more broadly to Jews from Central and Eastern Europe.