Ingomar is a small unincorporated community in southeastern Rosebud County, Montana, United States, along the route of U.S. Route 12. The town was established in 1908, as a station stop on the Chicago, Milwaukee, St. Paul and Pacific Railroad, then under construction in Montana. Although the land around Ingomar attracted numerous homesteaders during the decade following the railroad's completion, the region proved to be far too arid and inhospitable for intensive agricultural use, and by the 1920s the town was in decline.