| Șimișna | |
| Pushpin Map: | Romania |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Cluj, Sălaj |
| Subdivision Type3: | Villages |
| Subdivision Name3: | Ciubanca, Hășmaș, Șimișna |
| Length: | 22km (14miles) |
| Mouth: | Someș |
| Mouth Location: | Rus |
| Mouth Coordinates: | 47.276°N 23.6131°W |
| Basin Size: | 137km2 |
| Tributaries Left: | Escu, Ceaca |
The Șimișna (Hungarian: Semesnye) is a left tributary of the river Someș in Romania. It discharges into the Someș near Rus. Its length is 22km (14miles) and its basin size is 137km2.