| Fâstâca | |
| Pushpin Map: | Romania |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Vaslui County |
| Subdivision Type3: | Villages |
| Subdivision Name3: | Fâstâci, Bălești |
| Length: | 11km (07miles) |
| Mouth: | Stemnic |
| Mouth Location: | Bălești |
| Mouth Coordinates: | 46.7214°N 27.5341°W |
| Progression: | Stemnic→ |
| Basin Size: | 29km2 |
The Fâstâca is a right tributary of the river Stemnic in Romania. It flows into the Stemnic in Bălești. Its length is 11km (07miles) and its basin size is 29km2.