Martinsdale is an unincorporated community and census-designated place in southeastern Meagher County, Montana, United States. As of the 2020 census, the population was 43. The town was a station stop on the now-abandoned transcontinental main line of the Chicago, Milwaukee, St. Paul and Pacific Railroad, and is a community center for nearby ranches and farms. Martinsdale was the home of the poet Grace Stone Coates, author of Black Cherries, Mead& Mangel-Wurzel, and Portulacas in the Wheat.