Judaism (from the Latin Iudaismus, derived from the Greek Ioudaïsmos, and ultimately from the Hebrew יהודה, Yehudah, "Judah"; in Hebrew: יהדות, Yahadut, the distinctive characteristics of the Judean ethnos) is the religion, philosophy and way of life of the Jewish people. Judaism is a monotheistic religion, with its main inspiration being based on or found in the Hebrew Bible (also known as the Tanakh) which has been explored in later texts, such as the Talmud. Judaism is considered by religious Jews to be the expression of the covenantal relationship God established with the Children of Israel.

Judaism is not a homogenous religion, and embraces a number of streams and views. Today, Rabbinic Judaism is the most numerous stream, and holds that God revealed his laws and commandments to Moses on Mount Sinai in the form of both the Written and Oral Torah. Historically, this assertion was challenged by various groups such as the Sadducees and Hellenistic Judaism during the Second Temple period; the Karaites and Sabbateans during the early and later medieval period; and among segments of the modern reform movements. Liberal movements in modern times such as Humanistic Judaism may be nontheistic. Today, the largest Jewish religious movements are Orthodox Judaism (Haredi Judaism and Modern Orthodox Judaism), Conservative Judaism and Reform Judaism. A major source of difference between these groups is their approach to Jewish law. Orthodox Judaism maintains that the Torah and Jewish law are divine in origin, eternal and unalterable, and that they should be strictly followed. Conservative and Reform Judaism are more liberal, with Conservative Judaism generally promoting a more "traditional" interpretation of Judaism's requirements than Reform Judaism. A typical Reform position is that Jewish law should be viewed as a set of general guidelines rather than as a set of restrictions and obligations whose observance is required of all Jews. Historically, special courts enforced Jewish law; today, these courts still exist but the practice of Judaism is mostly voluntary. Authority on theological and legal matters is not vested in any one person or organization, but in the sacred texts and rabbis and scholars who interpret them.