| Rhondda to Olympia Heights (Florida) | 4,295.70 mi (6,913.27 km) |
| Rhondda to Omaha (Nebraska) | 4,166.10 mi (6,704.69 km) |
| Rhondda to On Top of the World Designated Place (Florida) | 4,209.19 mi (6,774.03 km) |
| Rhondda to Onalaska (Wisconsin) | 3,862.14 mi (6,215.52 km) |
| Rhondda to Oneida (New York) | 3,292.20 mi (5,298.28 km) |
| Rhondda to Oneonta (New York) | 3,293.92 mi (5,301.06 km) |
| Rhondda to Ontario (California) | 5,308.00 mi (8,542.40 km) |
| Rhondda to Ontario (Oregon) | 4,733.63 mi (7,618.04 km) |
| Rhondda to Opa-locka (Florida) | 4,283.29 mi (6,893.29 km) |
| Rhondda to Opelika (Alabama) | 4,163.18 mi (6,700.00 km) |
| Rhondda to Opelousas (Louisiana) | 4,543.36 mi (7,311.83 km) |
| Rhondda to Orange (California) | 5,328.42 mi (8,575.26 km) |
| Rhondda to Orange (Texas) | 4,631.67 mi (7,453.96 km) |
| Rhondda to Orange City (Florida) | 4,175.57 mi (6,719.93 km) |
| Rhondda to Orangeburg (South Carolina) | 3,936.21 mi (6,334.72 km) |
