14 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Round Rock | 1 | 139,055 | 120,572 | 2.73% | 3,667 | 38 | City |
| Georgetown | 2 | 109,502 | 68,712 | 8.05% | 1,883 | 58 | City |
| Cedar Park | 3 | 78,465 | 78,037 | 0.11% | 3,065 | 26 | City |
| Hutto | 4 | 46,304 | 28,086 | 8.54% | 3,322 | 14 | City |
| Taylor | 5 | 18,230 | 16,438 | 2% | 809 | 23 | City |
| Liberty Hill | 6 | 14,052 | 3,712 | 17.26% | 3,032 | 5 | City |
| Sonterra | 7 | 10,102 | 3,912 | 7.14% | 4,271 | 2 | CDP |
| Jarrell | 8 | 5,986 | 1,811 | 16.21% | 1,674 | 4 | City |
| Serenada | 9 | 1,708 | 1,415 | 0.23% | 793 | 2 | CDP |
| Florence | 10 | 1,218 | 1,183 | 0.58% | 1,334 | 1 | City |
| Granger | 11 | 1,215 | 1,185 | 0.5% | 1,822 | 1 | City |
| Thrall | 12 | 885 | 823 | 1.37% | 1,903 | 0 | City |
| Weir | 13 | 786 | 704 | 2.08% | 432 | 2 | City |
| Coupland | 14 | 305 | 289 | 0.99% | 158 | 2 | City |
Round Rock is the largest city in Williamson County, with a population of 139,055.
Coupland is the smallest city in Williamson County, with a population of 305.
There are 14 cities in Williamson County, Texas.