The men's 100 metre butterfly competition of the swimming events at the 2015 Pan American Games took place on July 16 at the CIBC Pan Am/Parapan Am Aquatics Centre and Field House in Toronto, Canada. The defending Pan American Games champion was Albert Subirats of Venezuela. This race consisted of two lengths of the pool, all lengths in butterfly. The top eight swimmers from the heats would qualify for the A final (where the medals would be awarded), while the next best eight swimmers would qualify for the B final.