There are 23 National Natural Landmarks in Ohio.
Map
| Name | Image | Date | Location | County | Ownership | Description |
|---|---|---|---|---|---|---|
| Arthur B. Williams Memorial Woods | 1974 | 41°33′44″N 81°25′36″W / 41.562282°N 81.426792°W | Cuyahoga | municipal | A remarkably pristine remnant beech-maple forest | |
| Blacklick Woods | 
|
1974 | 39°56′14″N 82°48′28″W / 39.937222°N 82.807778°W | Fairfield | county | An outstanding example of relatively undisturbed, old-growth beech-maple and swamp forest communities |
| Brown's Lake Bog | 
|
1967 | 40°40′51″N 82°03′45″W / 40.6809°N 82.0624°W | Wayne | private | One of the few well-preserved, virgin boreal acid bogs remaining in a region where wetlands have been drained for agricultural use. |
| Buzzardroost Rock, Lynx Prairie, The Wilderness | 
|
1967 | 38°45′34″N 83°24′25″W / 38.759381°N 83.407013°W | Adams | private | Supports many rare or uncommon species and it has an almost 50- year history of scientific observations. |
| Cedar Bog | 
|
1967 | 40°03′34″N 83°47′44″W / 40.059444°N 83.795556°W | Champaign | state | An excellent example of a marl swamp. Part of Cedar Bog State Nature Preserve. |
| Clear Fork Gorge | 
|
1967 | 40°36′40″N 82°17′13″W / 40.610982°N 82.286827°W | Ashland | state | Clearly illustrates evidence of stream reversal due to the Wisconsin glacier. Located in Mohican State Park. |
| Clifton Gorge | 
|
1967 | 39°47′38″N 83°49′53″W / 39.793903°N 83.831525°W | Greene | state | Exemplary of interglacial and postglacial canyon-cutting into the dolomites of the Niagara Escarpment. Part of Clifton Gorge State Nature Preserve. |
| Crall Woods | 1974 | 41°01′42″N 82°26′04″W / 41.028219°N 82.434376°W | Ashland | private | A near-virgin remnant of maple-basswood-beech forest-type. | |
| Cranberry Bog | 
|
1968 | 39°55′54″N 82°28′06″W / 39.931545°N 82.468232°W | Licking | state | The only known bog of its type in existence. Part of Cranberry Bog State Nature Preserve. |
| Dysart Woods | 
|
1967 | 39°59′05″N 80°59′51″W / 39.9846°N 80.9976°W | Belmont | state | One of the finest remaining examples of the white oak forests of eastern Ohio. Managed by Ohio University. |
| Fort Hill State Memorial | 
|
1974 | Hillsboro39°06′47″N 83°24′23″W / 39.1131°N 83.4063°W | Highland | state | Excellent outcrops of Silurian, Devonian, and Mississippian sedimentary bedrock and a natural bridge. |
| Glacial Grooves State Memorial | 
|
1967 | 41°36′59″N 82°42′23″W / 41.616304°N 82.70652°W | Erie | state | Very large limestone glacial grooves. |
| Glen Helen Natural Area | 
|
1965 | 39°48′15″N 83°52′54″W / 39.804125°N 83.881697°W | Greene | private | Includes a waterfall that carved a large travertine bowl around its pool. |
| Goll Woods | 
|
1974 | 41°33′15″N 84°21′42″W / 41.554294°N 84.361738°W | Fulton | state | One of the best remaining examples of an oak-hickory dominated forest in Ohio. Part of Goll Woods State Nature Preserve. |
| Hazelwood Botanical Preserve | 1974 | Hamilton | state | Highly detailed study of the site's plant ecology was published in 1929. Managed by the University of Cincinnati. | ||
| Highbanks Natural Area | 
|
1980 | 40°08′38″N 83°01′42″W / 40.143889°N 83.028333°W | Delaware, Franklin | county | A forested bluff overlooking the Olentangy River. |
| Holden Natural Area | 1967 | Geauga, Lake | private | A complex of three natural areas. | ||
| Hueston Woods | 
|
1967 | 39°34′21″N 84°44′29″W / 39.5725°N 84.741389°W | Butler, Preble | state | A noteworthy example of beech-maple climax forest that has never been cut. Located in Hueston Woods State Park. |
| Mantua Swamp | 1976 | 41°16′49″N 81°12′41″W / 41.280278°N 81.211389°W | Portage | private | Contains many different wetland communities. | |
| Mentor Marsh | .jpg)
|
1964 | 41°43′45″N 81°18′20″W / 41.729164°N 81.305492°W | Lake | state | Consists of marsh vegetation, aquatic plants, swamp and bottomland forest, and upland forest. Part of Mentor Marsh State Nature Preserve. |
| Serpent Mound Cryptoexplosive Structure | 
|
1980 | 39°02′00″N 83°24′00″W / 39.033333°N 83.4°W | Adams, Highland, Pike | private | A structure of undetermined origin exposed by differential erosion. |
| Tinker's Creek Gorge | 
|
1967 | 41°21′54″N 81°36′35″W / 41.365°N 81.609722°W | Cuyahoga | municipal | Contains a virgin oak-hickory and virgin beech-maple-hemlock forest. |
| White Pine Bog Forest | 1976 | Geauga | municipal, private | The only remaining near-virgin remnant white pine boreal bog in Ohio. |