The Hebrew Bible is made up of 24 books. The Old Testament used by Christians consists of the same books as those of the Hebrew Bible, but they are arranged differently and many books are divided, resulting in more books in the Old Testament than in the Hebrew Bible.

Among Christians, the Old Testament varies between Protestantism and Roman Catholicism: Protestants include 39 books in the Old Testament while Roman Catholics add seven books, called the Apocrypha, to their version, for a total of 46 books. The books of the Apocrypha resemble those of the Old Testament, but since they were written later than most of the Old Testament (probably 300 B.C.-A.D. 70), both Protestants and Jews treat them separately. The Bibles used by all three religions—Judaism, Roman Catholicism, and Protestantism—begin with the same seven books: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua, and Judges. The first five of these were written by Moses.