John Vernon Diener (January 23, 1887 – May 29, 1937) was mayor of Green Bay, Wisconsin.
Diener was born in Baraboo, Wisconsin, in 1887. He graduated from Notre Dame Law School before moving to Green Bay. Diener later practiced law with future U.S. Representative Thomas F. Konop. In 1914, Diener married Margaret Wigman. They had six children. During World War I, he served as an officer in the United States Army with the 119th Infantry Regiment of the 30th Infantry Division. Diener died in 1937.
Diener was mayor from 1929 to 1937. Previously, he was an unsuccessful candidate for district attorney of Brown County, Wisconsin. He was a Democrat.