William McMahon is a former Hong Kong international lawn bowler.
McMahon represented Hong Kong at two Commonwealth Games; in the fours event at the 1990 Commonwealth Games and in the pairs event at the 1994 Commonwealth Games.
In 1987 he won a triples silver medal at the Asia Pacific Bowls Championships in Lae, Papua New Guinea.
His wife Rosemary McMahon was also an international lawn bowler and his son is Mark McMahon.