James Barney Marsh (April 12, 1856 – June 26, 1936) was an American engineer and bridge designer. He patented a new design for arch bridges. Marsh gave Archie Alexander, the first African-American to graduate as an engineer from Iowa State University, his first job. Marsh worked in the bridge building business for over 50 years, and several of his bridges are listed in the National Register of Historic Places.