- Macedonia (1,385 Companies)
- Macksburg (12 Companies)
- Madeira (21 Companies)
- Madison (1,390 Companies)
- Madison Township (2 Companies)
- Madison Twp (2 Companies)
- Magnetic Springs (2 Companies)
- Magnolia (173 Companies)
- Maineville (899 Companies)
- Malaga (3 Companies)
- Malinta (32 Companies)
- Malta (114 Companies)
- Malvern (193 Companies)
- Manchester (176 Companies)
- Mansfield (8,572 Companies)
- Mantua (496 Companies)
- Maple Heights (1,140 Companies)
- Maplewood (16 Companies)
- Marblehead (11 Companies)
- Marengo (303 Companies)
- Maria Stein (185 Companies)
- Marietta (3,907 Companies)
- Marion (4,557 Companies)
- Mark Center (7 Companies)
- Marshallville (83 Companies)
- Martin (20 Companies)
- Martins Ferry (1,099 Companies)
- Martinsburg (15 Companies)
- Martinsville (53 Companies)
- Marysville (2,819 Companies)
- Mason (3,700 Companies)
- Massillon (3,565 Companies)
- Masury (249 Companies)
- Matamoras (1 Company)
