Noahidism (/ˈnoʊəhaɪdɪzəm/) or Noachidism (/ˈnoʊəxaɪdɪzəm/) is a monotheistic Jewish religious movement aimed at non-Jews, based upon the Seven Laws of Noah and their traditional interpretations within Orthodox Judaism.

According to the Jewish law, non-Jews (gentiles) are not obligated to convert to Judaism, but they are required to observe the Seven Laws of Noah to be assured of a place in the World to Come (Olam Ha-Ba), the final reward of the righteous. The penalty for violating any of the Noahide laws is discussed in the Talmud, but in practical terms it is subject to the working legal system which is established by the society at large. Those who subscribe to the observance of the Noahic Covenant are referred to as Bnei Noach (Hebrew: בני נח, "Sons of Noah") or Noahides (/ˈnoʊ.əhaɪdz/). The modern Noahide movement was founded in the 1990s by Orthodox Jewish rabbis from Israel, mainly tied to Chabad-Lubavitch and religious Zionist organizations, including the Temple Institute.

Historically, the Hebrew term Bnei Noach has been applied to all non-Jews as descendants of Noah. However, nowadays it is primarily used to refer specifically to those "Righteous Gentiles" who observe the Seven Laws of Noah. Noahide communities have spread and developed primarily in the United States, United Kingdom, Latin America, Nigeria, the Philippines, and Russia. According to a Noahide source in 2018^[update], there are over 20,000 official Noahides around the world and the country with the greatest number is the Philippines.

The scriptural and theological basis for the seven commandments of the Noahic Covenant is said to be derived interpretatively from demands addressed to Adam and to Noah, who are believed to be the progenitors of humankind in Judaism, and therefore to be regarded as universal moral laws. The seven commandments of the Noahic Covenant enumerated in the Babylonian Talmud (Avodah Zarah 8:4, Sanhedrin 56a-b) are:

According to the American Roman Catholic priest and dogmatic theologian Bruce R. Barnes, the obligation to follow the Noahic Covenant and its seven commandments was incumbent upon the Jewish people as well, and remained effective for them until the Ten Commandments were given to Moses on Mount Sinai:

With the giving of the Torah, God chose a people to live by His Commandments. This is a critical moment for those who believe that revelation is the only authentic expression of law. Such individuals think that the Revealed Law predominates and that the Noahide Laws are absorbed into the Mosaic Laws, thereby losing their independence. This unification of the two sets of law during the revelation at Sinai strengthened and confirmed (rather than diminished) the obligation for non-Jews to follow the Noahide Laws. Righteous Gentiles were obliged to follow the Seven Commandments and, by association, the Sinaitic Commandments because the Noahide Laws were now considered subsumed into the Sinai Laws. This did not alter the distinction between the two sets of people who followed the respective laws. [...] The relationship between the Noahites and the Jews would always be similar to the relationship between a priest and a faithful layman. The obligation to follow the Noahide Laws was incumbent upon the Jews from Adam to the Revelation at Sinai. Virtually all Jewish thinkers who dealt with this issue kept this in mind.

The concept of "Righteous Gentiles" (gerim toshavim) has a few precedents in the history of Judaism, primarily during Biblical times and the Roman domination of the Mediterranean. In the Hebrew Bible, it is reported that the legal status of ger toshav (Biblical Hebrew: גר תושב, ger: "foreigner" or "alien" + toshav: "resident", lit. 'resident alien') was granted to those Gentiles (non-Jews) living in the Land of Israel who did not want to convert to Judaism but agreed to observe the Seven Laws of Noah. The Sebomenoi or God-fearers of the Roman Empire were another ancient example of non-Jews being included within the Jewish community without converting to Judaism.

During the Golden Age of Jewish culture in the Iberian Peninsula, the medieval Jewish philosopher and rabbi Moses Maimonides (1135–1204) wrote in the halakhic legal code Mishneh Torah that Gentiles (non-Jews) must perform exclusively the Seven Laws of Noah and refrain from studying the Torah or performing any Jewish commandment, including resting on the Shabbat; however, Maimonides also states that if Gentiles want to perform any Jewish commandment besides the Seven Laws of Noah according to the correct halakhic procedure, they are not prevented from doing so. According to Maimonides, teaching non-Jews to follow the Seven Laws of Noah is incumbent on all Jews, a commandment in and of itself. Nevertheless, the majority of rabbinic authorities over the centuries have rejected Maimonides' opinion, and the dominant halakhic consensus has always been that Jews are not required to spread the Noahide laws to non-Jews.