| Holyhead to Oak Harbor (Washington) | 4,537.08 mi (7,301.73 km) |
| Holyhead to Oak Hills (Oregon) | 4,698.72 mi (7,561.86 km) |
| Holyhead to Oak Lawn (Illinois) | 3,734.86 mi (6,010.68 km) |
| Holyhead to Oak Park (California) | 5,224.42 mi (8,407.90 km) |
| Holyhead to Oak Park (Illinois) | 3,728.12 mi (5,999.83 km) |
| Holyhead to Oak Park (Michigan) | 3,526.02 mi (5,674.58 km) |
| Holyhead to Oak Ridge (Florida) | 4,134.79 mi (6,654.30 km) |
| Holyhead to Oak Ridge (New Jersey) | 3,249.69 mi (5,229.86 km) |
| Holyhead to Oak Ridge (Tennessee) | 3,876.28 mi (6,238.27 km) |
| Holyhead to Oakdale (California) | 5,085.04 mi (8,183.58 km) |
| Holyhead to Oakdale (Minnesota) | 3,772.93 mi (6,071.94 km) |
| Holyhead to Oakland (California) | 5,124.89 mi (8,247.71 km) |
| Holyhead to Oakland (New Jersey) | 3,239.48 mi (5,213.45 km) |
| Holyhead to Oakland Park (Florida) | 4,201.00 mi (6,760.86 km) |
| Holyhead to Oakleaf Plantation (Florida) | 4,065.50 mi (6,542.79 km) |
