Population groups in Israel are the major ethnic groups of Jews and Arabs. The major religions--Judaism, Islam, and Christianity, and Druze--are often used officially as "ethnic" classifications.

In many instances, Israel also allows the immediate non-Jewish family of immigrants to immigrate and acquire citizenship in the law know as the Law of Return. For the purposes of the Law of Return, anyone with a Jewish grandparent or who converted to Judaism is considered Jewish, and Israeli law also allows the immediate non-Jewish family of immigrants to immigrate. This definition is not the same as that in traditional Jewish law; it is a deliberately wider, so as to include those non-Jewish relatives of Jews who were perceived to be Jewish.

"Who is a Jew?"

See main article Who is a Jew?

Jewish law defines a Jew as someone who is either the child of a Jewish mother, or a person who converts to Judaism in accord with Jewish law. This view is accepted by Orthodox Judaism. According to historians, this standard has been followed in some form for at least 1,000 years. This definition of Jewishness is still followed by all of Orthodox Judaism, Conservative Judaism, and most of Reform Judaism outside of the USA.

In the last half of the 20th century, two theologically liberal (primarily American) Jewish groups Reform Judaism and Reconstructionist Judaism have allowed people who do not meet these criteria to define themselves as Jews. They no longer require converts to follow traditional Jewish procedures of conversion, and they accept a person as a Jew even if their mother is non-Jewish, so long as the father is a Jew and the child is raised as a Jew.

This has resulted in a serious schism among the Jewish people; today many Reform Jewish and secular Jewish-Americans consider themselves Jews, although they are not considered Jewish by Orthodox Jews, Conservative Jews, and even by many Reform Jews outside of the United States.

This same schism exists in Israel, in which Jewishness for religious purposes is determined by the Chief Rabbinate of Israel. It follows Orthodox Jewish definitions of Jewishness. Also, Israel's Interior Ministry generally has the same criteria as the Orthodox rabbinate for considering someone as Jewish, and thus there are a large number of people who have immigrated under the Law of Return, but are not considered Jewish by the Rabbinate or the Interior Ministry. Thus, many population groupings put out by the Israeli government include a category "Jewish and other", which includes these people.