City | 2024 Population |
|---|---|
| Oak Creek | 37,374 |
| Oak Grove | 979 |
| Oakdale | 305 |
| Oakfield | 1,058 |
| Oakland | 1,051 |
| Oasis | 399 |
| Oconomowoc | 18,827 |
| Oconomowoc Lake | 588 |
| Oconto | 4,622 |
| Oconto Falls | 2,997 |
| Odanah | 75 |
| Ogdensburg | 181 |
| Ogema | 263 |
| Ojibwa | 334 |
| Okauchee Lake | 4,890 |
| Oliver | 417 |
| Oma | 327 |
| Omro | 3,612 |
| Onalaska | 19,068 |
| Oneida | 4,526 |
| Ontario | 537 |
| Oostburg | 3,111 |
| Orange | 551 |
| Oregon | 11,828 |
| Orfordville | 1,485 |
| Orienta | 176 |
| Orion | 532 |
| Osborn | 1,221 |
| Osceola | 2,903 |
| Oshkosh | 65,987 |
| Osseo | 1,779 |
| Otsego | 665 |
| Ottawa | 3,640 |
| Otter Creek | 517 |
| Oulu | 595 |
| Owen | 905 |
| Oxford | 534 |