Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Madison-Stewart Historic District | Park | 179 | Hamilton | 39 09 39 N | 084 23 50 W |
| Madisonburg | Populated Place | 352 | Wayne | 40 51 28 N | 081 55 33 W |
| Madisonburg Cemetery | Cemetery | 346 | Wayne | 40 51 39 N | 081 55 24 W |
| Madisonville | Populated Place | 184 | Hamilton | 39 09 27 N | 084 23 28 W |
| Madisonville Baptist Church | Church | 179 | Hamilton | 39 09 33 N | 084 23 34 W |
| Madisonville Branch Library | Building | 179 | Hamilton | 39 09 34 N | 084 23 34 W |
| Madisonville Church of Christ | Church | 241 | Hamilton | 39 10 45 N | 084 24 30 W |
| Madisonville Church of God | Church | 177 | Hamilton | 39 09 05 N | 084 22 49 W |
| Madisonville Medical Center | Hospital | 181 | Hamilton | 39 09 38 N | 084 23 29 W |
| Madisonville Post Office (historical) | Post Office | 182 | Hamilton | 39 09 30 N | 084 23 30 W |
| Madisonville Senior Citizens Center | Building | 180 | Hamilton | 39 09 42 N | 084 23 36 W |
| Madisonville United Methodist Church | Church | 184 | Hamilton | 39 09 38 N | 084 23 21 W |
| Madisonville Wesleyan Church | Church | 182 | Hamilton | 39 09 43 N | 084 24 35 W |
| Madland (historical) | Populated Place | 190 | Scioto | 38 45 48 N | 082 40 55 W |
| Madland Post Office (historical) | Post Office | 191 | Scioto | 38 45 50 N | 082 40 55 W |
| Madonna Hall | Building | 202 | Lucas | 41 42 42 N | 083 42 25 W |
| Madonna Hall | Hospital | 203 | Cuyahoga | 41 30 22 N | 081 37 52 W |
| Madriver Post Office (historical) | Post Office | 265 | Clark | 39 53 45 N | 083 55 30 W |
| Magadore High School | School | 341 | Summit | 41 02 53 N | 081 23 39 W |
| Magee Marsh | Swamp | 175 | Ottawa | 41 36 51 N | 083 10 20 W |
| Magee Marsh Wildlife Area | Park | 174 | Ottawa | 41 36 51 N | 083 09 50 W |
| Magic City Shopping Center | Locale | 297 | Summit | 41 00 55 N | 081 36 15 W |
| Maglott Hall | Building | 292 | Hardin | 40 45 59 N | 083 49 55 W |
| Magnetic Springs | Populated Place | 284 | Union | 40 21 10 N | 083 15 41 W |
| Magnetic Springs Post Office | Post Office | 285 | Union | 40 21 15 N | 083 15 45 W |
| Magnetic Springs United Methodist Church | Church | 284 | Union | 40 21 11 N | 083 15 41 W |
| Magnetic Springs Village Hall | Building | 285 | Union | 40 21 18 N | 083 15 47 W |
| Magnificant High School | School | 213 | Cuyahoga | 41 28 07 N | 081 51 01 W |
| Magnolia | Populated Place | 292 | Stark | 40 39 04 N | 081 17 56 W |
| Magnolia Airport | Airport | 301 | Stark | 40 39 35 N | 081 18 09 W |
| Magnolia Cemetery | Cemetery | 302 | Stark | 40 39 20 N | 081 17 46 W |
| Magnolia Elementary School | School | 299 | Stark | 40 39 14 N | 081 17 34 W |
| Magnolia Post Office | Post Office | 292 | Stark | 40 39 05 N | 081 17 54 W |
| Magnolia-Wade Park Historic District | Park | 202 | Cuyahoga | 41 30 57 N | 081 36 35 W |
| Magruder Hospital | Hospital | 177 | Ottawa | 41 30 20 N | 082 55 59 W |
| Magruder Memorial Heliport | Airport | 177 | Ottawa | 41 30 20 N | 082 55 58 W |
| Magsig Junior High School | School | 299 | Montgomery | 39 37 39 N | 084 09 59 W |
| Magyar Evangelical Reformed Church | Church | 338 | Stark | 40 55 00 N | 081 05 39 W |
| Magyar Reformed Church | Church | 192 | Ashtabula | 41 57 41 N | 080 33 13 W |
| Magyar United Church of Christ | Church | 220 | Lorain | 41 21 51 N | 082 06 60 W |
| Maher Park | Park | 247 | Fairfield | 39 42 35 N | 082 36 31 W |
| Mahler Museum | Building | 242 | Cuyahoga | 41 21 57 N | 081 50 58 W |
| Maholm Elementary School | School | 260 | Licking | 40 03 05 N | 082 25 25 W |
| Mahoning | Populated Place | 290 | Portage | 41 15 32 N | 081 02 55 W |
| Mahoning Avenue Historic District | Park | 273 | Trumbull | 41 14 20 N | 080 49 19 W |
| Mahoning Country Club | Locale | 305 | Trumbull | 41 09 18 N | 080 40 53 W |
| Mahoning County | Civil | 332 | Mahoning | 41 02 00 N | 080 45 59 W |
| Mahoning County Courthouse | Building | 260 | Mahoning | 41 05 57 N | 080 39 03 W |
| Mahoning County Experimental Farm | Locale | 351 | Mahoning | 41 00 37 N | 080 45 44 W |
| Mahoning County Fairgrounds | Locale | 357 | Mahoning | 41 00 45 N | 080 45 17 W |
| Mahoning County Joint Vocational School Airport | Airport | 343 | Mahoning | 41 02 03 N | 080 46 54 W |
| Mahoning Creek | Stream | | Portage | 41 15 50 N | 081 02 52 W |
| Mahoning Duck Hunters Club Pond | Reservoir | 306 | Mahoning | 40 58 24 N | 080 40 59 W |
| Mahoning Duck Hunters Club Pond Dam | Dam | 306 | Mahoning | 40 58 24 N | 080 40 59 W |
| Mahoning Golf Course | Locale | 307 | Trumbull | 41 09 32 N | 080 40 59 W |
| Mahoning Law Library | Building | 260 | Mahoning | 41 05 57 N | 080 39 03 W |
| Mahoning Plaza Shopping Center | Locale | 325 | Mahoning | 41 06 08 N | 080 42 30 W |
| Mahoning Post Office (historical) | Post Office | 289 | Portage | 41 15 30 N | 081 02 54 W |
| Mahoning River | Stream | | Mahoning | 40 57 29 N | 080 22 43 W |
| Mahoning Road Plaza | Locale | 332 | Stark | 40 48 58 N | 081 20 05 W |
| Mahoning United Methodist Church | Church | 314 | Mahoning | 41 06 11 N | 080 41 36 W |
| Maiden Lane Church of God | Church | 289 | Clark | 39 55 43 N | 083 49 50 W |
| Maidlow Cemetery | Cemetery | 235 | Putnam | 41 02 36 N | 083 58 16 W |
| Main 270 Shopping Center | Locale | 249 | Franklin | 39 57 19 N | 082 50 15 W |
| Main Avenue Viaduct | Bridge | 175 | Cuyahoga | 41 29 55 N | 081 42 18 W |
| Main Cemetery | Cemetery | 220 | Ashtabula | 41 46 58 N | 080 58 38 W |
| Main Chapel | Church | 225 | Franklin | 39 49 28 N | 082 56 27 W |
| Main Hill | Summit | 268 | Fairfield | 39 42 48 N | 082 35 58 W |
| Main Street Beach | Beach | 175 | Erie | 41 23 51 N | 082 33 05 W |
| Main Street Beach | Beach | 176 | Erie | 41 25 30 N | 082 21 59 W |
| Main Street Bridge | Bridge | 216 | Franklin | 39 57 22 N | 083 00 23 W |
| Main Street Christian Church | Church | 207 | Morgan | 39 38 56 N | 081 51 20 W |
| Main Street Church of God | Church | 268 | Fairfield | 39 42 52 N | 082 37 23 W |
| Main Street Elementary School | School | 296 | Clinton | 39 17 41 N | 083 59 04 W |
| Main Street Elementary School | School | 238 | Franklin | 39 57 26 N | 082 57 37 W |
| Main Street Historic District | Park | 232 | Greene | 39 36 32 N | 084 00 30 W |
| Main Street Historic District | Park | 212 | Wood | 41 22 29 N | 083 39 02 W |
| Main Street United Brethren Church | Church | 188 | Wood | 41 35 26 N | 083 29 35 W |
| Main Street United Methodist Church | Church | 381 | Belmont | 39 59 17 N | 081 10 45 W |
| Main Street United Methodist Church | Church | 395 | Richland | 40 45 07 N | 082 30 59 W |
| Maineville | Populated Place | 247 | Warren | 39 18 54 N | 084 13 15 W |
| Maineville Cemetery | Cemetery | 248 | Warren | 39 18 53 N | 084 12 31 W |
| Mainsville | Populated Place | 308 | Perry | 39 42 44 N | 082 14 32 W |
| Maize Manor United Methodist Church | Church | 269 | Franklin | 40 02 43 N | 082 59 22 W |
| Maize Road Baptist Church | Church | 271 | Franklin | 40 03 09 N | 082 59 19 W |
| Maize Road Elementary School | School | 272 | Franklin | 40 03 14 N | 082 59 13 W |
| Majestic Concert Hall (historical) | Building | 168 | Hamilton | 39 06 06 N | 084 30 47 W |
| Majestic Mine | Mine | 346 | Harrison | 40 15 23 N | 080 52 53 W |
| Maketewah Country Club | Locale | 180 | Hamilton | 39 10 51 N | 084 28 11 W |
| Malabar Farm State Park | Park | 351 | Richland | 40 39 16 N | 082 24 25 W |
| Malabar Middle School | School | 429 | Richland | 40 43 49 N | 082 31 17 W |
| Malabu Lake | Reservoir | 339 | Jefferson | 40 16 24 N | 080 44 59 W |
| Malabu Lake Dam | Dam | 339 | Jefferson | 40 16 24 N | 080 44 59 W |
| Malaga | Populated Place | 402 | Monroe | 39 51 17 N | 081 08 57 W |
| Malaga Post Office | Post Office | 400 | Monroe | 39 51 15 N | 081 08 59 W |
| Malasia Park | Park | 341 | Summit | 41 04 11 N | 081 27 55 W |
| Malcom Cemetery | Cemetery | 304 | Highland | 39 04 38 N | 083 42 19 W |
| Malcom Cemetery | Cemetery | 294 | Williams | 41 38 14 N | 084 44 47 W |
| Malek Park | Park | 196 | Ashtabula | 41 56 50 N | 080 35 29 W |
| Malinta | Populated Place | 209 | Henry | 41 19 21 N | 084 02 17 W |
| Malinta Post Office | Post Office | 209 | Henry | 41 19 20 N | 084 02 15 W |
| Malinta-Grelton Elementary School | School | 209 | Henry | 41 19 25 N | 084 02 10 W |
| Mallard Club Marsh | Swamp | 175 | Lucas | 41 41 04 N | 083 20 46 W |
| Mallard Club Marsh State Wildlife Area | Park | 175 | Lucas | 41 40 45 N | 083 20 45 W |
| Mallet Creek | Populated Place | 308 | Medina | 41 10 02 N | 081 55 32 W |
| Mallet Creek | Stream | | Medina | 41 12 55 N | 081 54 35 W |
| Mallett Creek Post Office (historical) | Post Office | 309 | Medina | 41 10 00 N | 081 55 29 W |
| Mallon School (historical) | School | 313 | Fayette | 39 32 21 N | 083 33 49 W |
| Malloons Creek | Stream | | Meigs | 39 03 41 N | 082 12 10 W |
| Mallow Cemetery | Cemetery | 237 | Ross | 39 25 43 N | 083 13 26 W |