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.

[1] The defending Pan American Games champion was Albert Subirats of Venezuela.

Each National Olympic Committee (NOC) was able to enter up to two entrants providing they had met the A standard (53.99) in the qualifying period (January 1, 2014 to May 1, 2015).

NOCs were also permitted to enter one athlete providing they had met the B standard (57.23) in the same qualifying period.

[2] All other competing athletes were entered as universality spots.