What are the oldest complete or nearly complete Bible manuscripts that we have? When were they written?
Surely we have one from the 1st or 2nd centuries? No, we do not.
How about the 3rd century? Unfortunately we do not have one from even this century.
The first manuscripts we have are the Codex Vaticanus and the Codex Sinaiticus from the 4th century.
Prior to this time, we have only have small fragments of parts of the Bible.
The Old Testament of the Codex Sinaiticus is in the Greek Septuagint version and contains deuterocanonical books which Protestants rejected in the 16th century as well as books in the New Testament which the Church determined to be non-inspired later in the 4th century:
The Greek Septuagint in the Codex includes books not found in the Hebrew Bible and regarded in the Protestant tradition as apocryphal, such as 2 Esdras, Tobit, Judith, 1 & 4 Maccabees, Wisdom and Sirach. Appended to the New Testament are the Epistle of Barnabas and ‘The Shepherd’ of Hermas.
The Codex Vaticanus also includes the deuterocanonical books, but several books from the New Testament are missing, possibly due to them deteriorating over the centuries or possibly because they were not included. It also seems possible that it contained non-canonical writings like 1st Clement.
Here again we have evidence of the canon of Scripture still being determined as late as the mid-300s. John Calvin claimed that the canon of Scripture was obvious to anyone with the Holy Spirit, as easily as discerning “black from white, sweet from bitter,” yet the historical reality demonstrates that it was not “self-evident” to any Christian; rather, the very human-looking process by which the canon was discerned took a long time, and in those centuries, many differing canonical lists were proposed. Most Protestants today mimic Calvin by saying that the canon is self-evident (my Evangelical friend John is one of them).
Some Protestants also claim that the Catholic Church manipulated and altered historical writings to make them seem to support the Church’s positions on doctrinal issues. But if that were true, how could we rely on the Bibles we have, given that the earliest extant manuscripts are these two codices that date from the 4th century? They are copies of copies of copies of the original 1st century writings, none of which we have today. Anytime in those hundreds of years, an apostate Church could have maliciously altered the Bible to say what it wanted it to say, but the fact is that the Church reverenced the Scriptures then as she does now, and they were amazingly faithfully preserved as they had been handed on. For 1500 years, Catholic monks devoted their lives to painstakingly copying the Bible by hand. The canard that the Catholic Church systemically manipulated historical writings to fit her own evil agenda is shown to be a specious falsehood.
What is cool is that earlier this month, a scholar found another fragment belonging to the Codex Sinaiticus in the book binding in a monastery–the portion of the first part of Joshua where he is talking about them entering the Promised Land.

Amen, very good post. I had a Protestant teacher mock the vulgate but then say we could trust our old testament because of Jerome’s accuracy and I never understood how he could claim both.
Important to note that we (Catholics) don’t accept all of the books mentioned above as scripture either (ex. esdras) and only cements the importance of a conciliar definition of the canon.