25 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rockford township | 1 | 166,516 | 170,214 | -0.3% | 1,500 | 111 | Township |
| Rockford | 2 | 144,420 | 148,670 | -0.59% | 2,219 | 65.08 | City |
| Harlem township | 3 | 38,738 | 39,209 | -0.13% | 1,186 | 32.67 | Township |
| Loves Park | 4 | 23,289 | 23,404 | -0.1% | 1,427 | 16.32 | City |
| Machesney Park | 5 | 22,428 | 22,932 | -0.45% | 1,768 | 12.69 | Village |
| Roscoe township | 6 | 20,000 | 20,220 | 0% | 652 | 30.68 | Township |
| Cherry Valley township | 7 | 19,003 | 19,331 | -0.17% | 627 | 30.30 | Township |
| Rockton township | 8 | 15,956 | 16,131 | -0.01% | 441 | 36.21 | Township |
| Roscoe | 9 | 10,767 | 10,957 | -0.35% | 1,049 | 10.27 | Village |
| South Beloit | 10 | 7,838 | 7,975 | -0.34% | 1,276 | 6.14 | City |
| Rockton | 11 | 7,712 | 7,851 | -0.36% | 1,124 | 6.86 | Village |
| Seward township | 12 | 6,834 | 6,656 | 0.4% | 196 | 34.95 | Township |
| Winnebago township | 13 | 4,881 | 4,979 | -0.25% | 148 | 32.93 | Township |
| Pecatonica township | 14 | 4,073 | 4,145 | -0.15% | 117 | 34.92 | Township |
| Owen township | 15 | 3,544 | 3,597 | -0.11% | 100 | 35.28 | Township |
| Winnebago | 16 | 2,843 | 2,922 | -0.56% | 1,470 | 1.93 | Village |
| Cherry Valley | 17 | 2,842 | 2,896 | -0.39% | 338 | 8.40 | Village |
| Durand township | 18 | 2,274 | 2,306 | -0.04% | 77 | 29.65 | Township |
| Pecatonica | 19 | 2,016 | 2,080 | -0.64% | 1,571 | 1.28 | Village |
| Durand | 20 | 1,358 | 1,390 | -0.44% | 1,478 | 0.92 | Village |
| Laona township | 21 | 1,250 | 1,265 | 0% | 46 | 27.08 | Township |
| Burritt township | 22 | 1,078 | 1,100 | -0.28% | 33 | 32.70 | Township |
| Shirland township | 23 | 947 | 967 | -0.32% | 49 | 19.20 | Township |
| Seward township | 24 | 826 | 843 | -0.24% | 23 | 35.81 | Township |
| Harrison township | 25 | 596 | 609 | -0.33% | 24 | 24.64 | Township |
Rockford township is the largest city in Winnebago County, with a population of 166,516.
Harrison township is the smallest city in Winnebago County.
There are 25 cities in Winnebago County, Illinois.