| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Wausau | 1 | 40,242 | 40,013 | 0.13% | 2,093 | 19 | City |
| Weston | 2 | 15,966 | 15,734 | 0.22% | 739 | 22 | Village |
| Kronenwetter | 3 | 8,430 | 8,364 | 0.2% | 163 | 52 | Village |
| Rib Mountain | 4 | 7,274 | 7,302 | 17.17% | 296 | 25 | Village |
| Rib Mountain | 5 | 7,274 | 7,302 | -0.08% | 296 | 25 | Village |
| Rib Mountain | 6 | 6,245 | 7,302 | 0.6% | 255 | 25 | Village |
| Rib Mountain | 7 | 6,245 | 7,302 | -14.22% | 255 | 25 | Village |
| Rothschild | 8 | 5,645 | 5,557 | 0.32% | 865 | 7 | Village |
| Mosinee | 9 | 4,547 | 4,454 | 0.4% | 579 | 8 | City |
| Maine | 10 | 2,623 | 2,606 | 0.08% | 61 | 43 | Village |
| Schofield | 11 | 2,345 | 2,176 | 1.47% | 1,109 | 2 | City |
| Spencer | 12 | 1,806 | 1,817 | -0.17% | 917 | 2 | Village |
| Stratford | 13 | 1,626 | 1,594 | 0.43% | 307 | 5 | Village |
| Marathon City | 14 | 1,541 | 1,578 | -0.39% | 472 | 3 | Village |
| Edgar | 15 | 1,421 | 1,442 | -0.28% | 786 | 2 | Village |
| Athens | 16 | 1,190 | 1,062 | 0% | 486 | 2 | Village |
| Hatley | 17 | 662 | 647 | 0.15% | 678 | 1 | Village |
| Unity | 18 | 366 | 377 | -0.54% | 369 | 1 | Village |
| Aniwa | 19 | 234 | 244 | -0.85% | 110 | 2 | Village |
| Eland | 20 | 193 | 198 | -0.52% | 87 | 2 | Village |
| Elderon | 21 | 148 | 156 | -1.33% | 132 | 1 | Village |
| Fenwood | 22 | 139 | 141 | -0.71% | 141 | 1 | Village |
Wausau is the largest city in Marathon County, with a population of 40,242.
Fenwood is the smallest city in Marathon County, with a population of 139.
There are 22 cities in Marathon County, Wisconsin.