Swimming at the 2007 World Aquatics Championships – Men's 100 metre butterfly

The men's 100 metre butterfly at the 2007 World Aquatics Championships took place on 30 March (heats, semifinals and a swim-off) and on the evening of 31 March (final) at Rod Laver Arena in Melbourne, Australia. 123 swimmers were entered in the event, of which 118 swam.

Existing records at the start of the event were:
 * World record (WR): 50.40, Ian Crocker (USA), 30 July 2005 in Montreal, Canada.
 * Championship record (CR): 50.40, Ian Crocker (USA), Montreal 2005 (30 July 2005)

Swim-off for 8th/Finals

 * 1) Jason Dunford (Kenya) — 51.85 (Q)
 * 2) Ryan Pini (Papua New Guinea) — 52.10