57 cities
| City | 2025 Pop. ↓ |
|---|---|
| Osaka | 18,921,600 |
| Okayama | 718,616 |
| Oita | 474,415 |
| Okazaki | 352,361 |
| Otsu | 298,164 |
| Odawara | 203,035 |
| Obihiro | 173,890 |
| Oyama | 159,936 |
| Ota | 152,104 |
| Ogaki | 150,570 |
| Ome | 149,323 |
| Otaru | 143,792 |
| Okinawa | 142,840 |
| Omuta | 131,974 |
| Onojo | 94,957 |
| Onomichi | 90,936 |
| Omura | 89,918 |
| Obu | 77,864 |
| Okegawa | 75,062 |
| Omihachiman | 69,189 |
| Odate | 64,543 |
| Otawara | 58,888 |
| Okaya | 54,286 |
| Oami | 53,239 |
| Oi | 50,593 |
| Ono | 50,230 |
| Obita | 45,293 |
| Onoda | 44,295 |
| Otofuke | 40,944 |
| Ojiya | 40,549 |
| Okawa | 39,223 |
| Ozu | 38,833 |
| Omagari | 38,805 |
| Ono | 37,469 |
| Ogawa | 37,443 |
| Ofunato | 35,418 |
| Okunoya | 34,627 |
| Obama | 32,896 |
| Oiso | 32,595 |
| Odacho-oda | 31,867 |
| Otsuki | 31,226 |
| Omachi | 30,599 |
| Otake | 30,151 |
| Ozu | 29,820 |
| Omiya | 27,588 |
| Ono-hara | 26,190 |
| Omigawa | 25,763 |
| Ogori-shimogo | 23,516 |
| Okawara | 23,340 |
| Okuchi-shinohara | 22,425 |
| Owase | 22,038 |
| Oyama | 21,744 |
| Omamacho-omama | 21,286 |
| Obanazawa | 20,821 |
| Ohara | 20,226 |
| Oarai | 19,326 |
| Otsuchi | 16,497 |