The Old Testament (abbreviated OT) is the first part of Christian Bibles based primarily upon the Hebrew Bible (or Tanakh), a collection of ancient religious writings by the Israelites believed by many Christians and religious Jews to be the sacred Word of God. Its counterpart is the New Testament, the second part of the Christian Bible. The books that comprise the Old Testament canon differ between Christian Churches as well as their order and names. The most common Protestant canon comprises 39 books, the Catholic canon comprises 46 books, and the canons of the Eastern Orthodox and Oriental Orthodox Churches comprise up to 51 books. The 39 books in common to all the Christian canons corresponds to 24 books of the Tanakh, with some differences of order, and there are some differences in text. The additional number reflects the split of texts in the Christian Bibles into separate books, for example, Kings, Samuel and Chronicles, Ezra–Nehemiah and the minor prophets into separate books. The books which are part of a Christian Old Testament but which are not part of the Hebrew canon are sometimes described as deuterocanonical. In general, Protestant bibles do not include deuterocanonical books in their canon, but some versions of Anglican and Lutheran bibles place such books in a separate section called Apocrypha.
The Old Testament consists of many distinct books by various authors produced over a period of centuries. The canon formed in stages, first the Pentateuch by around 400 BC, then the Prophets during the Hasmonean dynasty (140-116 BC), and finally the remaining books.