Dunbar is an unincorporated community and former railroad depot village in Green Castle Township, Marshall County, Iowa, United States.

Dunbar was platted in 1882 in Greencastle Township, halfway between LeGrand and Gilman.

Dunbar also had a post office and general store in that era.

[1] The Chicago, Milwaukee, St. Paul and Pacific Railroad served Dunbar from 1881 until 1980.

This article about the geography of Marshall County, Iowa is a stub.