| Code | Name | Region |
|---|---|---|
| JPOIS | Oiso | 14 |
| JPOIT | Oita | 44 |
| JPOJI | Ojika | 42 |
| JPOJS | Ojiya | 15 |
| JPOYA | Ojoya | 46 |
| JPOAA | Okada | 13 |
| JPOKD | Okadama Apt/sapporo | 1 |
| JPOKM | Okamoto | 32 |
| JPOMR | Okamura | 38 |
| JPOMX | Ohama, Tottori | 31 |
| JPOHT | Ohata | 2 |
| JPOBX | Ohbe, Kagawa | 37 |
| JPOBS | Ohbishima | 33 |
| JPOKR | Ohbukura/uwajima | 38 |
| JPODN | Ohdana | 46 |
| JPOFR | Ohfukaura | 39 |
| JPOFK | Ohfunakoshi | 42 |
| JPOFT | Ohfunato | 3 |
| JPOOG | Ohgaki | 34 |
| JPOSR | Ohgasari | 46 |
| JPOGE | Ohge | 38 |
| JPOGS | Ohgishima | 14 |
| JPOGU | Ohgushi | 42 |
| JPOHO | Ohi | 13 |
| JPOIG | Ohigawa | 22 |
| JPOKH | Ohkawara | 42 |
| JPONE | Ohnejime | 46 |
| JPONS | Ohnishi/ohsaki | 34 |
| JPOON | Ohnoh | 45 |
| JPOFO | Ofunato | 3 |
| JPOFU | Ofunatu | 3 |
| JPOAG | Oga | 5 |
| JPOGG | Ogaki | 21 |
| JPOGA | Ogasawara | 13 |
| JPOAT | Ogatsu | 4 |
| JPOSG | Ogi | 41 |
| JPOII | Ogi, Ishikawa | 17 |
| JPOGK | Ogi, Kagawa | 37 |
| JPOGI | Ogi, Niigata | 15 |
| JPOGF | Ogifushi | 1 |
| JPOGH | Oginohama | 4 |
| JPOGM | Ogomori | 46 |
| JPOGO | Ogori | 40 |
| JPGGO | Ogose, Saitama | 11 |
| JPOHI | Oguchi-cho | 23 |
| JPOHM | Ohama, Ehime | 38 |
| JPOHA | Ohama, Kagawa | 37 |
| JPKHM | Ohama, Kagoshima | 46 |
| JPOOH | Ohama, Okayama | 33 |
| JPNYK | Nyukou | 32 |