Dominic John Grehan Mahony MBE (born 26 April 1964) is a British former modern pentathlete.
He competed in the 1988 Summer Olympics and at the 1992 Summer Olympics, winning a bronze medal at the 1988 Games.Mahony was appointed Member of the Order of the British Empire (MBE) in the 2014 New Year Honours for voluntary services to modern pentathlon.