Elwyn John Nicholson (December 11, 1923 – September 28, 2014) was a grocery store owner from Jefferson Parish, Louisiana, who served as a Democrat in the Louisiana State Senate from District 8 from 1972 to 1988 during the first three administrations of Governor Edwin Edwards and the interceding term of Republican David C. Treen. He was best known for his advocacy of the creation of Jean Lafitte National Historical Park and Barataria Preserve.