| Name | What | Region | Country | Lat | Long | Elev ft. | Pop est |
|---|---|---|---|---|---|---|---|
| An Oghmagh | city | Fermanagh and Omagh | United Kingdom | 54.60 | -7.29 | 255 | 3129 |
| An Omaigh | city | Fermanagh and Omagh | United Kingdom | 54.60 | -7.29 | 255 | 3129 |
| An Onneg | city | Bretagne | France | 48.59 | -1.84 | 16 | 6882 |
| An Oriant | city | Bretagne | France | 47.75 | -3.37 | 16 | 98722 |
| An Ospital | city | Bretagne | France | 48.33 | -4.24 | 101 | 6206 |
| An Oulmeg | city | Bretagne | France | 48.45 | -1.73 | 331 | 4802 |