| Merthyr Tudful to Oakley (California) | 5,210.35 mi (8,385.25 km) |
| Merthyr Tudful to Oakton (Virginia) | 3,538.38 mi (5,694.48 km) |
| Merthyr Tudful to Oakville (Missouri) | 4,080.67 mi (6,567.21 km) |
| Merthyr Tudful to Oatfield (Oregon) | 4,815.24 mi (7,749.38 km) |
| Merthyr Tudful to Ocala (Florida) | 4,199.87 mi (6,759.04 km) |
| Merthyr Tudful to Ocean Acres (New Jersey) | 3,376.37 mi (5,433.74 km) |
| Merthyr Tudful to Ocean City (New Jersey) | 3,410.40 mi (5,488.50 km) |
| Merthyr Tudful to Ocean Pines (Maryland) | 3,472.04 mi (5,587.70 km) |
| Merthyr Tudful to Ocean Pointe (Hawaii) | 7,161.04 mi (11,524.58 km) |
| Merthyr Tudful to Ocean Springs (Mississippi) | 4,413.88 mi (7,103.45 km) |
| Merthyr Tudful to Oceanside (California) | 5,339.68 mi (8,593.38 km) |
| Merthyr Tudful to Oceanside (New York) | 3,311.42 mi (5,329.22 km) |
| Merthyr Tudful to Ocoee (Florida) | 4,203.62 mi (6,765.08 km) |
| Merthyr Tudful to Oconomowoc (Wisconsin) | 3,793.17 mi (6,104.51 km) |
| Merthyr Tudful to Odenton (Maryland) | 3,505.52 mi (5,641.59 km) |
