Judaism (from the Latin Iudaismus, derived from the Greek Ioudaïsmos, and ultimately from the Hebrew יהודה, Yehudah, "Judah"; in Hebrew: יַהֲדוּת, Yahadut, the distinctive characteristics of the Judean ethnos) is a monotheistic religion originating in the Hebrew Bible (also known as the Tanakh) and explored in later texts such as the Talmud. It has been defined ethnically as "the religion, philosophy, and way of life of the Jews" and religiously as "a covenant between God and the Jewish people that can be traced back to the prophets Abraham and Moses".Rabbinic Judaism holds that God revealed his laws and commandments to Moses on Mount Sinai in the form of both the Written and Oral Torah. This assertion was historically challenged by the Karaites, a movement that flourished in the medieval period, which retains several thousand followers today and maintains that only the Written Torah was revealed. In modern times, liberal movements such as Humanistic Judaism may be nontheistic.

Judaism claims a historical continuity spanning more than 3,000 years. It is one of the oldest monotheistic religions, and the oldest to survive into the present day. The Hebrews / Israelites were already referred to as "Jews" in later books of the Tanakh such as the Book of Esther, with the term Jews replacing the title "Children of Israel". Judaism's texts, traditions and values strongly influenced later Abrahamic religions, including Christianity, Islam and the Baha'i Faith. Many aspects of Judaism have also directly or indirectly influenced secular Western ethics and civil law.

Jonathan Henry Sacks, Baron Sacks, Kt (born 8 March 1948, London) is the Chief Rabbi of the United Hebrew Congregations of the Commonwealth. His Hebrew name is Yaakov Zvi. As the spiritual head of the United Synagogue, the largest synagogue body in the UK, he is the Chief Rabbi of the British Orthodox synagogues, but he is not a religious authority for the Federation of Synagogues or the Union of Orthodox Hebrew Congregations or the other movements, Masorti, Reform and Liberal Judaism.

He is married with three children. One of his daughters, Gila Sacks, is a former Special Adviser to Gordon Brown.

Sacks was educated at St Mary's Primary School and Christ's College Finchley, Gonville & Caius College, Cambridge (MA), New College, Oxford, King's College London (PhD), Jews' College London and Etz Chaim Yeshiva (London).

In addition to the PhD he earned at King's College, he has also been awarded honorary doctorates from the universities of: Cambridge; Glasgow; Haifa; Middlesex; Yeshiva University; Liverpool and St. Andrews, Roehampton University and is an honorary fellow of Gonville and Caius and King's College London.