| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Round Rock | 1 | 145,048 | 120,556 | 2.67% | 3,756 | 39 | City |
| Georgetown | 2 | 115,088 | 68,725 | 7.65% | 1,953 | 59 | City |
| Cedar Park | 3 | 79,172 | 78,042 | 0.18% | 3,093 | 26 | City |
| Hutto | 4 | 49,696 | 28,091 | 7.92% | 3,329 | 15 | City |
| Taylor | 5 | 18,779 | 16,446 | 2.05% | 820 | 23 | City |
| Liberty Hill | 6 | 15,377 | 3,680 | 15.47% | 3,318 | 5 | City |
| Jarrell | 7 | 6,710 | 1,785 | 14.31% | 1,876 | 4 | City |
| Florence | 8 | 1,253 | 1,193 | 0.64% | 1,372 | 1 | City |
| Granger | 9 | 1,236 | 1,185 | 0.65% | 1,853 | 1 | City |
| Thrall | 10 | 899 | 823 | 1.47% | 1,933 | 0 | City |
| Weir | 11 | 807 | 704 | 1.89% | 443 | 2 | City |
| Coupland | 12 | 307 | 289 | 0.66% | 159 | 2 | City |
Round Rock is the largest city in Williamson County, with a population of 145,048.
Coupland is the smallest city in Williamson County, with a population of 307.
There are 12 cities in Williamson County, Texas.