13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fairfield | 1 | 123,335 | 119,890 | 0.56% | 2,966 | 42 | City |
| Vallejo | 2 | 122,861 | 125,930 | -0.5% | 4,037 | 30 | City |
| Vacaville | 3 | 104,455 | 102,147 | 0.44% | 3,497 | 30 | City |
| Suisun City | 4 | 29,648 | 29,478 | 0.11% | 7,403 | 4 | City |
| Benicia | 5 | 26,319 | 27,107 | -0.6% | 2,054 | 13 | City |
| Dixon | 6 | 20,532 | 19,352 | 1.16% | 2,892 | 7 | City |
| Rio Vista | 7 | 10,308 | 10,008 | 0.59% | 1,562 | 7 | City |
| University California-Davis | 8 | 8,840 | 9,031 | 2.36% | 5,119 | 2 | CDP |
| Hartley | 9 | 2,881 | 2,655 | 0.88% | 445 | 6 | CDP |
| Allendale | 10 | 1,814 | 1,429 | 1.17% | 296 | 6 | CDP |
| Green Valley | 11 | 1,576 | 1,583 | -0.25% | 188 | 8 | CDP |
| El Macero | 12 | 1,266 | 1,086 | 7.11% | 2,157 | 1 | CDP |
| Elmira | 13 | 129 | 234 | -3.01% | 243 | 1 | CDP |
Fairfield is the largest city in Solano County, with a population of 123,335.
Elmira is the smallest city in Solano County, with a population of 129.
There are 13 cities in Solano County, California.