The Parthenon’s peristyle is surrounded by 46 columns.
The outer colonnade follows the standard formula of an octastyle temple: eight columns stand across each short end, while seventeen columns run along each long side. Counting those rows separately gives 8 + 8 + 17 + 17, but the four corner columns belong to both an end and a side. Subtracting those duplicated corners leaves 46 distinct exterior columns.
This arrangement is one of the Parthenon’s defining features. The building is a Doric peripteral temple, meaning that a continuous ring of columns surrounds its central architectural mass. It is also unusually broad for a Doric temple because it has eight columns on each façade instead of the more familiar six.
The number 46 refers only to the outer peristyle. It should not be confused with the temple’s interior colonnades, which supported the roof and helped frame the cella. Some descriptions therefore give additional column counts when discussing the whole building, but 46 is the canonical answer for the columns surrounding the peristyle.