| Holyhead to Odessa (Texas) | 4,779.94 mi (7,692.57 km) |
| Holyhead to Ogden (Utah) | 4,612.68 mi (7,423.40 km) |
| Holyhead to Oildale (California) | 5,161.83 mi (8,307.17 km) |
| Holyhead to Ojus (Florida) | 4,212.80 mi (6,779.85 km) |
| Holyhead to Okemos (Michigan) | 3,562.15 mi (5,732.73 km) |
| Holyhead to Oklahoma City (Oklahoma) | 4,411.16 mi (7,099.08 km) |
| Holyhead to Okmulgee (Oklahoma) | 4,347.09 mi (6,995.96 km) |
| Holyhead to Olathe (Kansas) | 4,137.16 mi (6,658.12 km) |
| Holyhead to Old Jamestown (Missouri) | 3,968.78 mi (6,387.13 km) |
| Holyhead to Oldsmar (Florida) | 4,207.57 mi (6,771.42 km) |
| Holyhead to Olean (New York) | 3,358.87 mi (5,405.59 km) |
| Holyhead to Olive Branch (Mississippi) | 4,144.03 mi (6,669.17 km) |
| Holyhead to Olivehurst (California) | 5,030.95 mi (8,096.53 km) |
| Holyhead to Olney (Maryland) | 3,437.83 mi (5,532.65 km) |
| Holyhead to Olympia (Washington) | 4,615.00 mi (7,427.12 km) |
