| Dolhir Formation | |
| Type: | Formation |
| Age: | Ashgill Series |
| Period: | Ordovician |
| Region: | Wales |
| Underlies: | Mudstones of the Fron Frys Formation. |
| Overlies: | Unconformable on various Caradoc Formations. |
| Thickness: | 490 metres. Lateral variations, 320 - 490 metres. |
| Extent: | Not defined |
The Dolhir Formation is a geologic formation in Wales. It preserves fossils dating back to the Ordovician period.