| Cașin | |
| Pushpin Map: | Romania |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Harghita, Covasna |
| Subdivision Type3: | Cities |
| Subdivision Name3: | Târgu Secuiesc |
| Length: | 54km (34miles) |
| Mouth: | Râul Negru |
| Mouth Coordinates: | 45.981°N 26.1678°W |
| Basin Size: | 482km2 |
| Tributaries Right: | Turia |
The Cașin is a right tributary of the river Râul Negru in Romania. It discharges into the Râul Negru in Catalina.[1] It flows through the villages and towns Plăieșii de Sus, Plăieșii de Jos, Iacobeni, Valea Seacă, Sânzieni, Târgu Secuiesc and Catalina. Its length is 54km (34miles) and its basin size is 482km2.
The following rivers are tributaries to the river Cașin (from source to mouth):