When were the 27 books of the New Testament first mentioned and by whom?

The 27 books of the New Testament were first mentioned together in a list by Athanasius, the Bishop of Alexandria, in his Easter letter of 367 AD. This letter is significant as it provides one of the earliest known references to the canonical collection of New Testament texts as we recognize them today. Athanasius' list was influential in shaping the canon, though the acceptance of these texts evolved over the following centuries.