| Official Name: | Trnjaci |
| Native Name: | Трњаци |
| Settlement Type: | Village (Selo) |
| Pushpin Map: | Serbia |
| Pushpin Label Position: | right |
| Subdivision Type: | Country |
| Subdivision Name: | Serbia |
| Subdivision Type1: | District |
| Subdivision Name1: | Kolubara District |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Ub |
| Unit Pref: | Metric |
| Area Footnotes: | [1] |
| Population As Of: | 2011 |
| Population Total: | 747 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
| Coordinates: | 44.4544°N 20.0897°W |
| Elevation M: | 138 |
Trnjaci (Serbian: Трњаци) is a village in the municipality of Ub in western Serbia. According to the 2011 census, the village has a population of 747 inhabitants.