Brețcu is a commune in Covasna County, Transylvania, Romania composed of three villages: Brețcu, Mărtănuș (Kézdimartonos), and Oituz (Ojtoztelep). The village has been recorded under different names: Bereczk (1476), Breczko (1482–1496), Bretzku, and Bereck (1854).
The Gârcin is a left tributary of the river Tărlung in Romania. The Tărlung itself is a tributary of the river Râul Negru.
The Săliște is a left tributary of the river Cibin in Romania. It discharges into the Cibin in Orlat. Its length is 32 km (20 mi) and its basin size is 220 km2 (85 sq mi).
The Tărlung is a left tributary of the river Râul Negru in Romania. It discharges into the Râul Negru in Băcel. Its length is 57 km (35 mi) and drains a basin spanning 485 km2 (187 sq mi).
The Covasna (Hungarian: Kovászna is a left tributary of the river Râul Negru in Romania. It joins the Râul Negru in Bita. Its length is 28 km and its basin size is 290 km2.
The Râul Negru is a left tributary of the river Olt in Romania. It joins the Olt in Lunca Câlnicului. The Râul Negru flows through the villages Lemnia, Lunga, Catalina, Hătuica, Surcea, Telechia, Bita, Reci, Sântionlunca, Ozun, Băcel, Chichiș and Lunca Câlnicului. Its length is 88 km (55 mi) and its basin size is 2,349 km2 (907 sq mi).
The Nimăiești is a right tributary of the river Crișul Negru in Romania. Its length is 26 km (16 mi) and its basin size is 109 km2 (42 sq mi). The 26 km long river discharges into the Crișul Negru in Beiuș.
The Cașin is a right tributary of the river Râul Negru in Romania. It discharges into the Râul Negru in Catalina. It flows through the villages and towns Plăieșii de Sus, Plăieșii de Jos, Iacobeni, Valea Seacă, Sânzieni, Târgu Secuiesc and Catalina. Its length is 54 km (34 mi) and its basin size is 482 km2 (186 sq mi).
The Doftana is a left tributary of the river Tărlung in Romania. The Tărlung in turn is a tributary of the river Râul Negru
The Lisnău is a left tributary of the Râul Negru in Romania. It flows into the Râul Negru near Lunca Ozunului. Its length is 11 km (6.8 mi) and its basin size is 23 km2 (8.9 sq mi).
The Zăbala is a left tributary of the Râul Negru in Romania. It flows into the Râul Negru near Surcea. Its length is 16 km (9.9 mi) and its basin size is 37 km2 (14 sq mi).
The Pădureni is a right tributary of the Râul Negru in Romania. It discharges into the Râul Negru near Bita. Its length is 24 km (15 mi) and its basin size is 53 km2 (20 sq mi).
The Finiș is a left tributary of the river Crișul Negru in Romania. It starts at the confluence of headwaters Bălăteasa and Izbucul. Its length is 23 km (14 mi) and its basin size is 87 km2 (34 sq mi). It discharges into the Crișul Negru in the village Finiș.
The Ghelința is a left tributary of the river Râul Negru in Romania. It discharges into the Râul Negru in Imeni. Its length is 21 km (13 mi) and its basin size is 99 km2 (38 sq mi).
The Ojdula is a left tributary of the Râul Negru in Romania. It flows into the Râul Negru near the city Târgu Secuiesc. Its length is 19 km (12 mi) and its basin size 48 km2 (19 sq mi).
The Estelnic is a right tributary of the Râul Negru in Romania. It flows into the Râul Negru near the village Lunga, east of Târgu Secuiesc. Its length is 20 km (12 mi) and its basin size is 89 km2 (34 sq mi).
The Teliu is a right tributary of the river Tărlung in Romania. The Tărlung in turn is a tributary of the river Râul Negru. The Teliu flows into the Tărlung near the village Teliu. Its length is 14 km (8.7 mi) and its basin size is 43 km2 (17 sq mi).
The Lemnia is a right tributary of the Râul Negru in Romania. It flows into the Râul Negru near the village Lemnia. Its length is 13 km (8.1 mi) and its basin size is 35 km2 (14 sq mi).
The Dalnic is a right tributary of the Râul Negru in Romania. It flows into the Râul Negru near Leț. Its length is 15 km (9.3 mi) and its basin size is 40 km2 (15 sq mi).
The Mărcușa is a right tributary of the Râul Negru in Romania. It flows into the Râul Negru between the villages Mărcușa and Surcea. Its length is 24 km (15 mi) and its basin size is 89 km2 (34 sq mi).
