Great uncial codices

The great uncial codices or four great uncials are the only remaining uncial codices that contain (or originally contained) the entire text of the Bible (Old and New Testament) in Greek. They are the Codex Vaticanus in the Vatican Library, the Codex Sinaiticus and the Codex Alexandrinus in the British Library, and the Codex Ephraemi Rescriptus in the Bibliothèque nationale de France in Paris.

Many other fragments exist of approximately 300 Greek New Testament uncial manuscripts on vellum. There are 45 uncials which were given sigla in the Gregory–Aland classification system due to their importance, including all of the great uncials. There are about 140 papyrus Greek New Testament fragments as well. There are old Biblical manuscripts in other languages like Syriac and Latin, but none of them are as old and as important as the oldest uncials, nor are they in the Greek of the New Testament writings.

What sets apart the great uncials are their age, their level of completion, and the opinions of Bible scholars who prefer them over other others, believing them to be closer to the autographs of the authors of the New Testament writings. Their nearly complete texts of the Bible also bears weight on the study of the development of the New Testament canon and how the Old Testament was used in the early Church. Their primary use is in textual criticism of New Testament manuscripts in which scholars study and debate textual variants in the New Testament.

After decades of scholarship in New Testament textual criticism, Kurt Aland and Barbara Aland introduced five categories of New Testament manuscripts in 1981 and placed two of the great uncials completely in Category I, the "manuscripts of a very special quality." Codex Alexandrinus was placed in Category III "manuscripts of a distinctive character" in the Gospels and Category I in the rest of the New Testament. The other, Codex Ephraemi Rescriptus, was placed in Category II, "manuscripts of a special quality" for its entirety.

This places two of the great uncials, Vaticanus and Sinaiticus, in the Alands' method of classification's highest and most important category, shared by only a handful of smaller uncials and a few dozen parchment fragments of this age. The two are often compared with one another due to their relevance.