| Coțatcu | |
| Pushpin Map: | Romania |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Buzău, Vrancea |
| Subdivision Type3: | Villages |
| Subdivision Name3: | Pleșești, Coțatcu, Voetin, Bălești |
| Length: | 41km (25miles) |
| Source1: | Căpățâna Hill |
| Source1 Location: | Buzău County |
| Source1 Coordinates: | 45.5203°N 26.9744°W |
| Source1 Elevation: | 414m (1,358feet) |
| Mouth: | Râmnicul Sărat |
| Mouth Location: | Vâjâitoarea |
| Mouth Coordinates: | 45.4944°N 27.3139°W |
| Mouth Elevation: | 29m (95feet) |
| Basin Size: | 321km2 |
| Tributaries Left: | Cireș, Slimnic |
| Tributaries Right: | Viroaga |
The Coțatcu is a left tributary of the river Râmnicul Sărat in Romania.[1] It discharges into the Râmnicul Sărat near Vâjâitoarea. Its length is 41km (25miles) and its basin size is 321km2.