Juan Diego Nelson y Duggan, also known as Jack Nelson (26 May 1891 – 7 August 1985 in Buenos Aires, Argentina), was an Olympic Argentinian polo player during the first half of the 20th century. He was of Irish descent and was educated at Beaumont College and the University of Buenos Aires. He is listed in the Argentinian polo team roster for the 1924 Summer Olympics which won the gold medal that year.
