Donald John Arnold (born July 14, 1935 in Kelowna, British Columbia) is a Canadian competition rower and Olympic champion.
He received a gold medal in coxless fours at the 1956 Summer Olympics in Melbourne, together with Archibald MacKinnon, Lorne Loomer and Walter D'Hondt.At the 1958 British Empire and Commonwealth Games Arnold received a gold medal in eights, and a silver medal in coxed fours.
He received a silver medal in eights at the 1960 Summer Olympics in Rome, as a member of the Canadian team.