12 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Farmerville | 1 | 3,355 | 3,456 | -0.59% | 580 | 6 | Town |
| Farmerville | 2 | 3,355 | 3,454 | -0.59% | 580 | 6 | Town |
| Bernice | 3 | 1,291 | 1,358 | -1% | 399 | 3 | Town |
| Bernice | 4 | 1,291 | 1,356 | -1% | 399 | 3 | Town |
| Marion | 5 | 595 | 624 | -1% | 185 | 3 | Town |
| Marion | 6 | 595 | 623 | -1% | 185 | 3 | Town |
| Spearsville | 7 | 119 | 126 | -1.65% | 50 | 2 | Village |
| Spearsville | 8 | 119 | 126 | -1.65% | 50 | 2 | Village |
| Lillie | 9 | 114 | 113 | 0% | 59 | 2 | Village |
| Lillie | 10 | 114 | 113 | 0% | 59 | 2 | Village |
| Downsville | 11 | 111 | 120 | -1.77% | 149 | 1 | Village |
| Downsville | 12 | 111 | 120 | -1.77% | 149 | 1 | Village |
Farmerville is the largest city in Union Parish, with a population of 3,355.
Downsville is the smallest city in Union Parish, with a population of 111.
There are 12 cities in Union Parish, Louisiana.