The Catholic Bible contains 73 books while the Protestant Bible contains 66 books. This is because Martin Luther removed 7 books from the Old Testament that were included in the Catholic Bible. These 7 books, known as the deuterocanonical books or Apocrypha, were part of the original Greek Septuagint translation of the Old Testament but were rejected by the Jewish Council of Jamnia in 90 AD and later by Protestant reformers like Martin Luther. However, Catholics maintain that the books were affirmed as part of the Bible by ecumenical councils of the Catholic Church in the 4th century.