John Eisenmann (March 26, 1851 – January 6, 1924), was an architect in Cleveland, Ohio.
As part of Eisenmann & Smith he designed the Cleveland Arcade in downtown Cleveland.
He also designed the Main building for Case School of Applied Science, present-day Case Western Reserve University, where he was also the school's first professor of civil engineering.
He pioneered structural steel construction in the United States and is credited with co-designing Cleveland's Arcade, "the first commercial building in the state designated an historic landmark in architecture." Eisenmann is also credited with designing the flag of Ohio in 1902.