| Niraj | |
| Map: | Raul Niraj.png |
| Subdivision Type1: | Country |
| Subdivision Name1: | Romania |
| Subdivision Type2: | Counties |
| Subdivision Name2: | Mureș County |
| Subdivision Type3: | Towns |
| Subdivision Name3: | Miercurea Nirajului, Ungheni |
| Length: | 82km (51miles) |
| Source1: | confluence of headwaters Nirajul Mare and Nirajul Mic. |
| Source1 Location: | Сâmpu Cetății |
| Source1 Coordinates: | 46.6742°N 25.0194°W |
| Mouth: | Mureș |
| Mouth Location: | near Ungheni |
| Mouth Coordinates: | 46.481°N 24.427°W |
| Basin Size: | 651km2 |
The Niraj (Hungarian: Nyárád; German: Niersch) is a river in the Gurghiu Mountains, Mureș County, northern Romania. Its name originates from the Hungarian word nyár, meaning "poplar". It is a left tributary of the river Mureș. It starts at the confluence of headwaters Nirajul Mare and Nirajul Mic. It flows through the villages Câmpu Cetății, Eremitu, Mătrici, Călugăreni, Dămieni, Grâușorul, Vărgata, Miercurea Nirajului, Dumitreștii, Gălești, Bolintineni, Păsăreni, Murgești, Acățari, Stejeriș, Crăciunești, Ilieni, Gheorghe Doja, Leordeni and joins the Mureș in Vidrasău, near the town Ungheni.[1] Its length is 82km (51miles) (including its source river Nirajul Mare) and its basin size is 651km2.
The following rivers are tributaries to the river Niraj (from source to mouth):