| Event name | County | Region |
|---|---|---|
| Oak Hill parkrun | Greater London | London |
| Oaklands parkrun | West Midlands | West Midlands |
| Oaklands College parkrun | Hertfordshire | East of England |
| Oakwell Hall parkrun | West Yorkshire | Yorkshire and The Humber |
| Old Deer Park parkrun | Greater London | London |
| Oldham parkrun | Greater Manchester | North West |
| Old Railway Trail parkrun, Llangollen | Clwyd | Wales |
| Omagh parkrun | County Tyrone | Northern Ireland |
| Orangefield parkrun | County Antrim | Northern Ireland |
| Oriam parkrun | Lothian | Scotland |
| Ormeau parkrun | County Antrim | Northern Ireland |
| Ormskirk parkrun | Lancashire | North West |
| Orpington parkrun | Greater London | London |
| Osterley parkrun | Greater London | London |
| Oxford parkrun | Oxfordshire | South East |