12 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Round Rock | 1 | 142,752 | 120,572 | 2.66% | 3,697 | 39 | City |
| Georgetown | 2 | 117,660 | 68,712 | 7.45% | 1,996 | 59 | City |
| Cedar Park | 3 | 78,551 | 78,037 | 0.11% | 3,068 | 26 | City |
| Hutto | 4 | 49,948 | 28,086 | 7.87% | 3,345 | 15 | City |
| Taylor | 5 | 18,589 | 16,438 | 1.97% | 812 | 23 | City |
| Liberty Hill | 6 | 16,120 | 3,712 | 14.72% | 3,479 | 5 | City |
| Jarrell | 7 | 6,821 | 1,811 | 13.95% | 1,907 | 4 | City |
| Florence | 8 | 1,225 | 1,183 | 0.57% | 1,342 | 1 | City |
| Granger | 9 | 1,221 | 1,185 | 0.49% | 1,831 | 1 | City |
| Thrall | 10 | 898 | 823 | 1.47% | 1,931 | 0 | City |
| Weir | 11 | 803 | 704 | 2.16% | 441 | 2 | City |
| Coupland | 12 | 308 | 289 | 0.98% | 160 | 2 | City |
Round Rock is the largest city in Williamson County, with a population of 142,752.
Coupland is the smallest city in Williamson County, with a population of 308.
There are 12 cities in Williamson County, Texas.