| Official Name: | Fatnassa |
| Native Name: | فطناسة |
| Pushpin Map: | Tunisia |
| Pushpin Label Position: | bottom |
| Subdivision Name: |  Tunisia |
| Subdivision Type1: | Governorate |
| Subdivision Name1: | Kébili |
| Subdivision Type2: | Municipality |
| Subdivision Name2: | Souk Lahad |
| Coordinates: | 33.7833°N 8.75°W |
Fatnassa is a small village in the Kebili Governorate in the south west of Tunisia. It belongs to the municipality (commune) of Souk Lahad.
The village is located by the southern shore of the Chott el Djerid, on the national highway RN16, crossing it. It is 13 km from Souk Lahad, 25 from Kébili, 52 from Degache, 54 from Douz and 68 from Tozeur.