| Diamond Bar to Orbetello | 6,249.80 mi (10,058.08 km) |
| Diamond Bar to Oria | 6,559.63 mi (10,556.71 km) |
| Diamond Bar to Oristano | 6,292.55 mi (10,126.88 km) |
| Diamond Bar to Orta Nova | 6,453.91 mi (10,386.57 km) |
| Diamond Bar to Orte | 6,286.90 mi (10,117.79 km) |
| Diamond Bar to Ortona | 6,356.96 mi (10,230.54 km) |
| Diamond Bar to Orvieto | 6,264.22 mi (10,081.29 km) |
| Diamond Bar to Orzinuovi | 6,052.97 mi (9,741.32 km) |
| Diamond Bar to Osimo | 6,266.74 mi (10,085.35 km) |
| Diamond Bar to Ospitaletto | 6,049.32 mi (9,735.43 km) |
| Diamond Bar to Ostuni | 6,545.02 mi (10,533.19 km) |
| Diamond Bar to Ottaviano | 6,441.20 mi (10,366.11 km) |
| Diamond Bar to Ovada | 6,050.79 mi (9,737.81 km) |
| Diamond Bar to Ozieri | 6,271.98 mi (10,093.77 km) |
| Diamond Bar to Paceco | 6,531.78 mi (10,511.88 km) |
