Edward John Duffy (6 June 1883 – 19 October 1918) was a South African athlete.
He competed at the 1908 Summer Olympics in London.
He was born in Ryno, North West and died in Johannesburg.
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.