14 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Round Rock | 1 | 136,977 | 120,549 | 2.46% | 3,612 | 37.92 | City |
| Georgetown | 2 | 114,687 | 68,749 | 8.71% | 1,972 | 58.15 | City |
| Cedar Park | 3 | 77,175 | 78,027 | -0.22% | 3,015 | 25.60 | City |
| Hutto | 4 | 45,887 | 28,081 | 8.41% | 3,292 | 13.94 | City |
| Taylor | 5 | 17,935 | 16,439 | 1.7% | 796 | 22.54 | City |
| Liberty Hill | 6 | 14,850 | 3,794 | 17.49% | 3,205 | 4.63 | City |
| Sonterra | 7 | 10,102 | 3,912 | 7.14% | 4,271 | 2.37 | CDP |
| Jarrell | 8 | 5,430 | 1,804 | 15.41% | 1,518 | 3.58 | City |
| Serenada | 9 | 1,708 | 1,415 | 0.23% | 793 | 2.15 | CDP |
| Florence | 10 | 1,215 | 1,185 | 0.5% | 1,331 | 0.91 | City |
| Granger | 11 | 1,199 | 1,184 | 0.25% | 1,798 | 0.67 | City |
| Thrall | 12 | 893 | 823 | 1.59% | 1,920 | 0.47 | City |
| Weir | 13 | 737 | 704 | 0.96% | 405 | 1.82 | City |
| Coupland | 14 | 299 | 288 | 0.67% | 155 | 1.93 | City |
Round Rock is the largest city in Williamson County, with a population of 136,977.
Coupland is the smallest city in Williamson County.
There are 14 cities in Williamson County, Texas.