13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fairfield | 1 | 121,391 | 119,833 | 0.26% | 2,919 | 41.59 | City |
| Vallejo | 2 | 120,749 | 125,894 | -0.84% | 3,967 | 30.43 | City |
| Vacaville | 3 | 102,815 | 102,092 | 0.14% | 3,442 | 29.87 | City |
| Suisun City | 4 | 28,253 | 29,478 | -0.86% | 7,054 | 4 | City |
| Benicia | 5 | 25,977 | 27,106 | -0.86% | 2,027 | 12.81 | City |
| Dixon | 6 | 19,493 | 19,032 | 0.47% | 2,745 | 7.10 | City |
| Rio Vista | 7 | 10,236 | 10,008 | 0.45% | 1,551 | 6.60 | City |
| University California-Davis | 8 | 8,840 | 9,031 | 2.36% | 5,119 | 1.73 | CDP |
| Hartley | 9 | 2,881 | 2,655 | 0.88% | 445 | 6.47 | CDP |
| Allendale | 10 | 1,814 | 1,429 | 1.17% | 296 | 6.14 | CDP |
| Green Valley | 11 | 1,576 | 1,583 | -0.25% | 188 | 8.37 | CDP |
| El Macero | 12 | 1,266 | 1,086 | 7.11% | 2,157 | 0.59 | CDP |
| Elmira | 13 | 129 | 234 | -3.01% | 243 | 0.53 | CDP |
Fairfield is the largest city in Solano County, with a population of 121,391.
Elmira is the smallest city in Solano County.
There are 13 cities in Solano County, California.