The earliest (4th c. CE) ms. containing almost the complete Christian Bible (757 vellum sheets) includes the bulk of the OT (except for most of Genesis & portions of 2 Samuel & Psalms) and the majority of NT books (notably lacking: the Pastoral letters & Revelation). This codex is listed in the earliest catalog of the papal library in the Vatican (1475). Its prior history is unknown. Since in many places Vaticanus supports the text of early papyri & one or another of Sinaiticus' scribes, modern scholars generally regard it as one of the most important mss. for establishing the original wording of NT passages.

[For more information see The Interpreter's Dictionary of the Bible vol. 4 (NY/Nashville: Abingdon Press, 1962), p. 747].

Other On-line resources:

• Manuscript Vat.gr.1209 - magnifiable digital images of the more than 1500 pages of Codex Vaticanus. 4th c. uncial text of Genesis begins on p. 42; the Gospel of Matthew on p. 1235, Mark on p. 1277and Luke on p. 1304 (posted by the Vatican Library). 

• Codex Vaticanus - photos & paleographical notes on John 1:3-4 posted by Timothy W. Seid [Interpreting Ancient Manuscripts].

• Codex Vaticanus - detailed history & description of the ms., listing omitted verses and phrases found in other biblical texts (Wikipedia).

• Codex Vaticanus - U. Benigni's article from the Catholic Encyclopedia (posted by New Advent).

• Codex Vaticanus - Michael Marlowe's notes with image & transcription of Matt 11:8-10 [Bible Research].