| Site name | Country | County | Nearest town | Site type | Access | Classification (girth in metres) | View on map |
|---|---|---|---|---|---|---|---|
| Oerley Hall – nr Rhydycroesau | England | Shropshire | Oswestry | garden | No | Ancient 4m-5m | View On Map |
| Offas Dyke – nr Maes-Treylow | Wales | Powys | Presteigne | historic site | Yes | Ancient 7m+ | View On Map |
| Offham | England | Kent | Maidstone | churchyard | Yes | Ancient 5m-7m | View On Map |
| Offranville | France | Seine-Maritime - Normandie | Dieppe | churchyard | Yes | Ancient 7m+ | View On Map |
| Offwell | England | Devon | Honiton | churchyard | Yes | Ancient 4m-5m | View On Map |
| Okeford Fitzpaine | England | Dorset | Sturminster Newton | churchyard | Yes | Ancient 5m-7m | View On Map |
| Old Alresford | England | Hampshire | Winchester | churchyard | Yes | Ancient 5m-7m | View On Map |
| Old Church Hotel | England | Cumbria | Penrith | former religious site | Yes | Ancient 7m+ | View On Map |
| Old Colwall | England | Herefordshire | Great Malvern | woodland | No | Ancient 7m+ | View On Map |
| Old Colwyn | Wales | Conwy | Colwyn Bay | footpath/road | Yes | Lost | View On Map |
| Old Coulsdon – Devilsden Wood | England | Greater London | Caterham | woodland | Yes | Notable | View On Map |
| Old Coulsdon churchyard | England | Greater London | London | churchyard | Yes | Notable | View On Map |
| Old Enton | England | Surrey | Godalming | woodland | No | Ancient 7m+ | View On Map |
| Old Glassinghall House | Scotland | Stirling | Dunblane | garden | Yes | Notable | View On Map |
| Old Heathfield | England | Sussex - East | Heathfield | churchyard | Yes | Ancient 4m-5m | View On Map |
| Old Oswestry Hill Fort | England | Shropshire | Oswestry | earthworks | Yes | Notable | View On Map |
| Old Pentland Cemetery | Scotland | Midlothian | Edinburgh | former religious site | Yes | Notable | View On Map |
| Old Radnor | Wales | Powys | Kington | churchyard | Yes | Lost, Notable | View On Map |
| Old Romney | England | Kent | Rye | churchyard | Yes | Ancient 4m-5m | View On Map |
| Old Sloden Wood | England | Hampshire | Ringwood | woodland | Yes | Notable | View On Map |