Who decided which books are in the Bible?

The popular version of this story is that a council, often the Council of Nicaea in 325 under the Emperor Constantine, voted on which books to include and suppressed the rest. It makes for a gripping novel, but almost every detail is false. Nicaea did not discuss, vote on, or even record raising the question of the canon; its business was the relationship of Christ to the Father. Historians across the spectrum, including the agnostic scholar Bart Ehrman, reject the Constantine myth outright.

What actually happened was slower and more careful. The canon was not decided in a single moment; it was recognized over centuries. Paul's letters were being collected in the first century. By around 180 the four Gospels were a fixed fact, and lists like the Muratorian Fragment already look substantially like our New Testament. Before Nicaea ever met, Eusebius shows a careful sorting of books already underway, using real criteria: apostolic origin, agreement with the church's inherited faith, and widespread use across the scattered churches. The disputed books were genuinely disputed for generations, which is evidence of care, not conspiracy. When councils like Hippo and Carthage listed the books at the end of the fourth century, they were ratifying a consensus long since reached, not voting books into being.

One honest caveat: Catholics, Orthodox, and Protestants still differ over a handful of Old Testament books, and both sides can point to ancient precedent. That is a real, reasonable disagreement this answer won't try to settle. But it touches only the margins, and it leaves the whole invented-by-an-emperor story untouched.