Edward John Duffy (6 June 1883 – 19 October 1918) was a South African athlete.
Duffy was a semifinalist (top 17) in the 100 metres at the 1908 Olympic Games, winning the first heat with a time of 11 3⁄5 seconds.
Duffy took third place in semifinal 3, losing to James Rector, the eventual silver medalist.
Duffy lost in the preliminary heats of the 200 metres, placing second to Harold Huff.
This biographical article relating to South African athletics is a stub.