Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| Irvington School (historical) | School | 259 | Adams | 38 56 31 N | 083 33 06 W |
| Irwin | Populated Place | 308 | Union | 40 07 21 N | 083 29 22 W |
| Irwin Church | Church | 202 | Lucas | 41 37 12 N | 083 46 48 W |
| Irwin Playground | Park | 230 | Montgomery | 39 46 12 N | 084 08 53 W |
| Irwin Post Office | Post Office | | Union | 40 07 20 N | 083 29 20 W |
| Irwin Prairie State Nature Preserve | Park | 203 | Lucas | 41 39 15 N | 083 46 46 W |
| Irwin School (historical) | School | 205 | Lucas | 41 37 47 N | 083 46 42 W |
| Isaac M Wise Temple | Church | 218 | Hamilton | 39 09 09 N | 084 29 07 W |
| Isaac R Ludwig Historical Mill | Locale | 195 | Lucas | 41 24 55 N | 083 51 45 W |
| Isaacs Creek | Stream | | Adams | 38 40 46 N | 083 37 36 W |
| Isaacs Run | Stream | | Knox | 40 31 12 N | 082 29 40 W |
| Isham Memorial Elementary School | School | 347 | Medina | 41 01 33 N | 081 44 20 W |
| Islamic Center Church | Church | 244 | Franklin | 39 58 01 N | 082 57 47 W |
| Islamic Center of Cleveland | Church | 204 | Cuyahoga | 41 28 48 N | 081 44 52 W |
| Islamic Center of Dayton | Church | 226 | Montgomery | 39 45 20 N | 084 10 34 W |
| Island | Populated Place | 340 | Mahoning | 40 54 54 N | 080 44 44 W |
| Island Creek | Populated Place | 250 | Jefferson | 40 27 10 N | 080 40 45 W |
| Island Creek | Stream | | Adams | 38 41 34 N | 083 34 28 W |
| Island Creek | Stream | | Jefferson | 40 25 43 N | 080 36 54 W |
| Island Creek | Stream | | Mahoning | 40 59 05 N | 081 00 28 W |
| Island Creek Boat Launch Ramp | Locale | 152 | Adams | 38 41 27 N | 083 35 01 W |
| Island Creek Cemetery | Cemetery | 389 | Jefferson | 40 27 53 N | 080 39 22 W |
| Island Creek Church | Church | 176 | Adams | 38 43 02 N | 083 34 39 W |
| Island Creek Post Office (historical) | Post Office | 250 | Jefferson | 40 27 10 N | 080 40 44 W |
| Island Creek Presbyterian Cemetery | Cemetery | 386 | Jefferson | 40 27 56 N | 080 39 21 W |
| Island Creek Presbyterian Church | Church | 390 | Jefferson | 40 27 56 N | 080 39 23 W |
| Island Creek School (historical) | School | 159 | Adams | 38 42 27 N | 083 34 55 W |
| Island Fishing Lakes | Reservoir | 264 | Butler | 39 26 30 N | 084 41 12 W |
| Island Fishing Lakes Dam | Dam | 264 | Butler | 39 26 30 N | 084 41 12 W |
| Island Grove Mill (historical) | Locale | 257 | Highland | 39 21 47 N | 083 22 39 W |
| Island Number 3 | Island | 247 | Miami | 40 00 31 N | 084 11 22 W |
| Island Park | Park | 204 | Defiance | 41 17 14 N | 084 20 19 W |
| Island Park | Park | 253 | Hancock | 40 54 04 N | 083 33 31 W |
| Island Park | Park | 225 | Montgomery | 39 46 40 N | 084 11 52 W |
| Island Park Dam | Dam | 223 | Montgomery | 39 46 30 N | 084 11 36 W |
| Island Park Reservoir | Reservoir | 223 | Montgomery | 39 46 30 N | 084 11 36 W |
| Island Pond | Reservoir | 278 | Butler | 39 26 49 N | 084 41 14 W |
| Island Run | Stream | | Morgan | 39 43 42 N | 081 54 12 W |
| Island School (historical) | School | 207 | Pickaway | 39 37 58 N | 082 57 26 W |
| Island View | Populated Place | 309 | Logan | 40 30 58 N | 083 53 10 W |
| Island View (subdivision) | Populated Place | 189 | Wood | 41 35 51 N | 083 34 16 W |
| Island View Park | Park | 187 | Wood | 41 36 05 N | 083 34 20 W |
| Island View Post Office (historical) | Post Office | 309 | Logan | 40 30 58 N | 083 53 10 W |
| Isle of Patmos Church | Church | 244 | Montgomery | 39 44 23 N | 084 14 15 W |
| Isle Saint George | Populated Place | 179 | Ottawa | 41 43 18 N | 082 49 13 W |
| Isle Saint George Post Office | Post Office | 178 | Ottawa | 41 43 20 N | 082 49 15 W |
| Isleboro Post Office (historical) | Post Office | 318 | Hocking | 39 26 05 N | 082 27 10 W |
| Isleta | Populated Place | 243 | Coshocton | 40 16 12 N | 081 40 17 W |
| Isleta Post Office (historical) | Post Office | 243 | Coshocton | 40 16 10 N | 081 40 19 W |
| Isleta United Methodist Church | Church | 246 | Coshocton | 40 15 53 N | 081 39 55 W |
| Islington Run | Stream | | Lawrence | 38 33 35 N | 082 44 34 W |
| Israel Baptist Church | Church | 181 | Butler | 39 23 32 N | 084 33 25 W |
| Israel Evangelical Lutheran Church | Church | 385 | Stark | 40 47 43 N | 081 09 53 W |
| Israel Temple Center | Church | 289 | Trumbull | 41 14 10 N | 080 47 23 W |
| Israelite Baptist Church | Church | 328 | Summit | 41 02 50 N | 081 30 56 W |
| Italian Pentecostal Church | Church | 204 | Cuyahoga | 41 28 10 N | 081 42 37 W |
| Italian Village Park | Park | 231 | Franklin | 39 58 39 N | 083 00 11 W |
| Ithaca | Populated Place | 315 | Darke | 39 56 14 N | 084 33 12 W |
| Ithaca Cemetery | Cemetery | 319 | Darke | 39 56 35 N | 084 33 35 W |
| Ithaca Lutheran Cemetery | Cemetery | 315 | Darke | 39 56 08 N | 084 33 06 W |
| Ithaca Post Office (historical) | Post Office | 315 | Darke | 39 56 15 N | 084 33 10 W |
| Ithaca United Methodist Church | Church | 316 | Darke | 39 56 22 N | 084 33 10 W |
| Iuka Park | Park | 250 | Franklin | 40 00 19 N | 082 59 56 W |
| Iuka Ravine Historic District | Park | 247 | Franklin | 40 00 18 N | 083 00 10 W |
| Iva Dale Subdivision | Populated Place | 170 | Gallia | 38 51 22 N | 082 08 49 W |
| Ivan D Troyer Farm Cemetery | Cemetery | 365 | Holmes | 40 31 32 N | 081 50 46 W |
| Ivan Terrell Memorial Fountain | Park | 252 | Miami | 40 02 22 N | 084 12 12 W |
| Ives Hall | Building | 224 | Franklin | 40 00 12 N | 083 00 60 W |
| Ivorydale | Populated Place | 161 | Hamilton | 39 10 39 N | 084 29 47 W |
| Ivorydale Junction | Populated Place | 152 | Hamilton | 39 10 12 N | 084 30 15 W |
| Ivorydale Post Office (historical) | Post Office | 161 | Hamilton | 39 10 40 N | 084 29 45 W |
| Ixworth (historical) | Populated Place | 186 | Butler | 39 22 00 N | 084 32 39 W |
| Izaak Walton Lake | Reservoir | 229 | Lawrence | 38 40 30 N | 082 35 06 W |
| Izaak Walton Lake Dam | Dam | 229 | Lawrence | 38 40 30 N | 082 35 06 W |
| J and B Sky Ranch Airport | Airport | 348 | Mahoning | 41 07 02 N | 080 31 21 W |
| J B Putnam Elementary School | School | 293 | Clinton | 39 17 52 N | 083 59 12 W |
| J C Donnell Memorial Stadium | Park | 240 | Hancock | 41 01 32 N | 083 39 16 W |
| J C Penney Catalog Outlet Store | Locale | 237 | Franklin | 39 55 47 N | 082 50 50 W |
| J C Williams Center | Building | 303 | Jefferson | 40 22 37 N | 080 37 13 W |
| J E Prass Elementary School | School | 302 | Montgomery | 39 40 44 N | 084 07 03 W |
| J F Burns Elementary School | School | 251 | Warren | 39 18 47 N | 084 17 08 W |
| J F Kennedy High School | School | 309 | Cuyahoga | 41 26 57 N | 081 33 37 W |
| J F Kennedy Park | Park | 262 | Franklin | 39 57 27 N | 082 48 22 W |
| J Glen Smith Health Center | Hospital | 187 | Cuyahoga | 41 32 24 N | 081 36 25 W |
| J M Stuart Power Plant | Building | 161 | Adams | 38 38 16 N | 083 41 35 W |
| J Otis Young Philosophy and Religion Building | Building | 292 | Hardin | 40 46 02 N | 083 49 44 W |
| J Stabler Ditch | Canal | 228 | Paulding | 41 05 23 N | 084 46 29 W |
| J W Galbreath Bicentennial Park | Park | 218 | Franklin | 39 57 22 N | 083 00 18 W |
| J W Reason Elementary School | School | 280 | Franklin | 40 02 00 N | 083 08 40 W |
| J-EM Farm Airport | Airport | 308 | Union | 40 09 15 N | 083 16 30 W |
| Jabe Grooms Hollow | Valley | | Pike | 39 01 55 N | 083 10 52 W |
| Jack D Hendricks Memorial Park | Park | 278 | Guernsey | 40 01 33 N | 081 34 49 W |
| Jack Martin Park | Park | 418 | Logan | 40 21 35 N | 083 44 26 W |
| Jack Nicklaus Sports Center | Locale | 243 | Warren | 39 20 38 N | 084 16 58 W |
| Jack Run | Stream | | Hocking | 39 30 48 N | 082 36 55 W |
| Jacklot Cemetery | Cemetery | 287 | Morgan | 39 43 54 N | 081 51 22 W |
| Jackman Cemetery | Cemetery | 323 | Columbiana | 40 41 51 N | 080 33 17 W |
| Jackman Elementary School | School | 189 | Lucas | 41 42 52 N | 083 35 38 W |
| Jackman School (historical) | School | 288 | Vinton | 39 12 47 N | 082 35 18 W |
| Jacko Run | Stream | | Jackson | 38 57 38 N | 082 43 52 W |
| Jacks Hollow Bridge | Bridge | 250 | Perry | 39 54 25 N | 082 10 07 W |
| Jacks Knob | Summit | 335 | Pike | 39 07 36 N | 083 06 32 W |
| Jackson | Populated Place | 211 | Jackson | 39 03 07 N | 082 38 12 W |
| Jackson | Populated Place | 363 | Morrow | 40 42 41 N | 082 44 45 W |
| Jackson | Populated Place | 316 | Wayne | 40 57 37 N | 081 53 58 W |
| Jackson (historical) | Populated Place | 260 | Muskingum | 39 57 20 N | 081 55 58 W |
| Jackson Assembly of God Church | Church | 218 | Jackson | 39 02 25 N | 082 37 47 W |
| Jackson Bog | Swamp | 307 | Stark | 40 51 24 N | 081 30 20 W |
| Jackson Bog State Nature Preserve | Park | 307 | Stark | 40 51 24 N | 081 30 21 W |
| Jackson Cemetery | Cemetery | 236 | Gallia | 38 43 18 N | 082 26 12 W |